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<!DOCTYPE html>    <html class='no-js' lang='en'><head> <meta content='IE=edge' http-equiv='X-UA-Compatible'> <meta charset='utf-8'> <meta content='width=device-width, initial-scale=1.0, maximum-scale=1, minimum-scale=1, user-scalable=no' name='viewport'> <meta content='en' name='Content-Language'> <link rel="stylesheet" media="screen" href="https://leanpub.com/assets/stylesheets/app-bundle-3a102529b44722ebfc51.css" /> <link rel="apple-touch-icon-precomposed" type="image/png" href="https://leanpub.com/assets/favicons/apple-touch-icon-57x57-3dc48b9be1873ac9bf6d580e7836e3e5.png" sizes="57x57" /> <link rel="apple-touch-icon-precomposed" type="image/png" href="https://leanpub.com/assets/favicons/apple-touch-icon-60x60-06b95deca3f378372b051ca8ea42cfbd.png" sizes="60x60" /> <link rel="apple-touch-icon-precomposed" type="image/png" href="https://leanpub.com/assets/favicons/apple-touch-icon-72x72-935ba702f9d3da9b4404aa2b797920e5.png" sizes="72x72" /> <link rel="apple-touch-icon-precomposed" 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o(n){if(e[n])return e[n].exports;var t=e[n]={exports:{},id:n,loaded:!1};return r[n].call(t.exports,t,t.exports,o),t.loaded=!0,t.exports}var e={};return o.m=r,o.c=e,o.p="",o(0)}([function(r,o,e){"use strict";var n=e(1),t=e(4);_rollbarConfig=_rollbarConfig||{},_rollbarConfig.rollbarJsUrl=_rollbarConfig.rollbarJsUrl||"https://cdnjs.cloudflare.com/ajax/libs/rollbar.js/2.5.2/rollbar.min.js",_rollbarConfig.async=void 0===_rollbarConfig.async||_rollbarConfig.async;var a=n.setupShim(window,_rollbarConfig),l=t(_rollbarConfig);window.rollbar=n.Rollbar,a.loadFull(window,document,!_rollbarConfig.async,_rollbarConfig,l)},function(r,o,e){"use strict";function n(r){return function(){try{return r.apply(this,arguments)}catch(r){try{console.error("[Rollbar]: Internal error",r)}catch(r){}}}}function t(r,o){this.options=r,this._rollbarOldOnError=null;var e=s++;this.shimId=function(){return e},"undefined"!=typeof window&&window._rollbarShims&&(window._rollbarShims[e]={handler:o,messages:[]})}function a(r,o){if(r){var e=o.globalAlias||"Rollbar";if("object"==typeof r[e])return r[e];r._rollbarShims={},r._rollbarWrappedError=null;var t=new p(o);return n(function(){o.captureUncaught&&(t._rollbarOldOnError=r.onerror,i.captureUncaughtExceptions(r,t,!0),i.wrapGlobals(r,t,!0)),o.captureUnhandledRejections&&i.captureUnhandledRejections(r,t,!0);var n=o.autoInstrument;return o.enabled!==!1&&(void 0===n||n===!0||"object"==typeof n&&n.network)&&r.addEventListener&&(r.addEventListener("load",t.captureLoad.bind(t)),r.addEventListener("DOMContentLoaded",t.captureDomContentLoaded.bind(t))),r[e]=t,t})()}}function l(r){return n(function(){var o=this,e=Array.prototype.slice.call(arguments,0),n={shim:o,method:r,args:e,ts:new Date};window._rollbarShims[this.shimId()].messages.push(n)})}var i=e(2),s=0,d=e(3),c=function(r,o){return new t(r,o)},p=function(r){return new d(c,r)};t.prototype.loadFull=function(r,o,e,t,a){var l=function(){var o;if(void 0===r._rollbarDidLoad){o=new Error("rollbar.js did not 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String(o)),o._rollbarContext=n()||{},o._rollbarContext._wrappedSource=r.toString(),window._rollbarWrappedError=o),o}},r._rollbar_wrapped._isWrap=!0,r.hasOwnProperty))for(var t in r)r.hasOwnProperty(t)&&(r._rollbar_wrapped[t]=r[t]);return r._rollbar_wrapped}catch(o){return r}};for(var u="log,debug,info,warn,warning,error,critical,global,configure,handleUncaughtException,handleUnhandledRejection,captureEvent,captureDomContentLoaded,captureLoad".split(","),f=0;f<u.length;++f)t.prototype[u[f]]=l(u[f]);r.exports={setupShim:a,Rollbar:p}},function(r,o){"use strict";function e(r,o,e){if(r){var t;if("function"==typeof o._rollbarOldOnError)t=o._rollbarOldOnError;else if(r.onerror){for(t=r.onerror;t._rollbarOldOnError;)t=t._rollbarOldOnError;o._rollbarOldOnError=t}var a=function(){var e=Array.prototype.slice.call(arguments,0);n(r,o,t,e)};e&&(a._rollbarOldOnError=t),r.onerror=a}}function n(r,o,e,n){r._rollbarWrappedError&&(n[4]||(n[4]=r._rollbarWrappedError),n[5]||(n[5]=r._rollbarWrappedError._rollbarContext),r._rollbarWrappedError=null),o.handleUncaughtException.apply(o,n),e&&e.apply(r,n)}function t(r,o,e){if(r){"function"==typeof r._rollbarURH&&r._rollbarURH.belongsToShim&&r.removeEventListener("unhandledrejection",r._rollbarURH);var n=function(r){var e,n,t;try{e=r.reason}catch(r){e=void 0}try{n=r.promise}catch(r){n="[unhandledrejection] error getting `promise` from event"}try{t=r.detail,!e&&t&&(e=t.reason,n=t.promise)}catch(r){}e||(e="[unhandledrejection] error getting `reason` from event"),o&&o.handleUnhandledRejection&&o.handleUnhandledRejection(e,n)};n.belongsToShim=e,r._rollbarURH=n,r.addEventListener("unhandledrejection",n)}}function a(r,o,e){if(r){var n,t,a="EventTarget,Window,Node,ApplicationCache,AudioTrackList,ChannelMergerNode,CryptoOperation,EventSource,FileReader,HTMLUnknownElement,IDBDatabase,IDBRequest,IDBTransaction,KeyOperation,MediaController,MessagePort,ModalWindow,Notification,SVGElementInstance,Screen,TextTrack,TextTrackCue,TextTrackList,WebSocket,WebSocketWorker,Worker,XMLHttpRequest,XMLHttpRequestEventTarget,XMLHttpRequestUpload".split(",");for(n=0;n<a.length;++n)t=a[n],r[t]&&r[t].prototype&&l(o,r[t].prototype,e)}}function l(r,o,e){if(o.hasOwnProperty&&o.hasOwnProperty("addEventListener")){for(var n=o.addEventListener;n._rollbarOldAdd&&n.belongsToShim;)n=n._rollbarOldAdd;var t=function(o,e,t){n.call(this,o,r.wrap(e),t)};t._rollbarOldAdd=n,t.belongsToShim=e,o.addEventListener=t;for(var a=o.removeEventListener;a._rollbarOldRemove&&a.belongsToShim;)a=a._rollbarOldRemove;var l=function(r,o,e){a.call(this,r,o&&o._rollbar_wrapped||o,e)};l._rollbarOldRemove=a,l.belongsToShim=e,o.removeEventListener=l}}r.exports={captureUncaughtExceptions:e,captureUnhandledRejections:t,wrapGlobals:a}},function(r,o){"use strict";function e(r,o){this.impl=r(o,this),this.options=o,n(e.prototype)}function n(r){for(var o=function(r){return function(){var o=Array.prototype.slice.call(arguments,0);if(this.impl[r])return this.impl[r].apply(this.impl,o)}},e="log,debug,info,warn,warning,error,critical,global,configure,handleUncaughtException,handleUnhandledRejection,_createItem,wrap,loadFull,shimId,captureEvent,captureDomContentLoaded,captureLoad".split(","),n=0;n<e.length;n++)r[e[n]]=o(e[n])}e.prototype._swapAndProcessMessages=function(r,o){this.impl=r(this.options);for(var e,n,t;e=o.shift();)n=e.method,t=e.args,this[n]&&"function"==typeof this[n]&&("captureDomContentLoaded"===n||"captureLoad"===n?this[n].apply(this,[t[0],e.ts]):this[n].apply(this,t));return this},r.exports=e},function(r,o){"use strict";r.exports=function(r){return function(o){if(!o&&!window._rollbarInitialized){r=r||{};for(var e,n,t=r.globalAlias||"Rollbar",a=window.rollbar,l=function(r){return new a(r)},i=0;e=window._rollbarShims[i++];)n||(n=e.handler),e.handler._swapAndProcessMessages(l,e.messages);window[t]=n,window._rollbarInitialized=!0}}}}]); // End Rollbar Snippet </script> <script src="https://www.google.com/recaptcha/api.js?render=6LdDCakUAAAAAEFI0Kyx_gg9t-G4r1mOWrIwFLd0"></script> <script src="https://leanpub.com/assets/modernizr-a38b94cc0625ba4488942166ee4d23a4.js"></script> </head> <body> <div id='react-root'></div> <div class='cookies-banner alert alert--info' style='display: none'> Leanpub requires cookies in order to provide you the best experience. <a class='dismiss link'>Dismiss</a> </div> <script type='text/javascript'> window.addEventListener('load', function() { var shouldShowCookies = document.cookie.indexOf('should_show_cookies') !== -1 if 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