Lazyloaded several required dependencies

- these dependencies can be pushed to be loaded later than upon boot,
  where boot time is critical
- this commit makes boot about 4% faster

ghost/core/core/frontend/helpers/comment_count.js

@@ -1,7 +1,9 @@
 const {SafeString} = require('../services/handlebars');
-const {html} = require('common-tags');
 
 module.exports = function commentCount(options) {
+    // Lazy require the dependency to keep boot fast
+    const {html} = require('common-tags');
+
     const empty = options.hash.empty === undefined ? '' : options.hash.empty;
     const singular = options.hash.singular === undefined ? 'comment' : options.hash.singular;
     const plural = options.hash.plural === undefined ? 'comments' : options.hash.plural;

ghost/core/ghost.js

@@ -12,15 +12,13 @@ process.env.NODE_ENV = process.env.NODE_ENV || 'development';
 const argv = process.argv;
 const mode = argv[2];
 
-const command = require('./core/cli/command');
-
 // Switch between boot modes
 switch (mode) {
 case 'repl':
 case 'timetravel':
 case 'generate-data':
 case 'record-test':
-    command.run(mode);
+    require('./core/cli/command').run(mode);
     break;
 default:
     // New boot sequence

ghost/email-content-generator/lib/EmailContentGenerator.js

@@ -1,7 +1,6 @@
 const _ = require('lodash').runInContext();
 const fs = require('fs-extra');
 const path = require('path');
-const htmlToText = require('html-to-text');
 
 _.templateSettings.interpolate = /{{([\s\S]+?)}}/g;
 
@@ -41,7 +40,8 @@ class EmailContentGenerator {
         const compiled = _.template(content);
         const htmlContent = compiled(data);
 
-        // generate a plain-text version of the same email
+        // lazyload the lib, and generate a plain-text version of the same email
+        const htmlToText = require('html-to-text');
         const textContent = htmlToText.fromString(htmlContent);
 
         return {

ghost/oembed-service/lib/OEmbedService.js

@@ -1,7 +1,6 @@
 const errors = require('@tryghost/errors');
 const tpl = require('@tryghost/tpl');
 const logging = require('@tryghost/logging');
-const cheerio = require('cheerio');
 const _ = require('lodash');
 const charset = require('charset');
 const iconv = require('iconv-lite');
@@ -297,6 +296,9 @@ class OEmbedService {
      * @returns {Promise<Object>}
      */
     async fetchOembedData(url, html, cardType) {
+        // Lazy require the library to keep boot quick
+        const cheerio = require('cheerio');
+
         // check for <link rel="alternate" type="application/json+oembed"> element
         let oembedUrl;
         try {