Enable ES2015 transpilation in client

Enable use of ES6 language features via Babel in the sidebar app and
annotator code.

 - Update Babelify to the current version
 - Add preset for transpiling ES2015

.babelrc

+{
+  "presets": ["es2015"],
+  "ignore": "**/vendor/*"
+}

gulpfile.js

@@ -102,17 +102,18 @@ var appBundles = [{
   // by the client.
   name: 'boot',
   entry: './src/boot/index',
+  transforms: ['babel'],
 },{
   // The sidebar application for displaying and editing annotations.
   name: 'app',
-  transforms: ['coffee'],
+  transforms: ['babel', 'coffee'],
   entry: './src/sidebar/app',
 },{
   // The annotation layer which handles displaying highlights, presenting
   // annotation tools on the page and instantiating the sidebar application.
   name: 'injector',
   entry: './src/annotator/main',
-  transforms: ['coffee'],
+  transforms: ['babel', 'coffee'],
 }];
 
 var appBundleConfigs = appBundles.map(function (config) {

package.json

@@ -17,7 +17,8 @@
     "angulartics": "0.17.2",
     "autofill-event": "0.0.1",
     "autoprefixer": "^6.0.3",
-    "babelify": "^6.1.3",
+    "babel-preset-es2015": "^6.24.0",
+    "babelify": "^7.3.0",
     "browserify": "^13.0.0",
     "browserify-istanbul": "^2.0.0",
     "browserify-ngannotate": "^1.0.1",

scripts/gulp/create-bundle.js

@@ -6,6 +6,7 @@
 var fs = require('fs');
 var path = require('path');
 
+var babelify = require('babelify');
 var browserify = require('browserify');
 var coffeeify = require('coffeeify');
 var exorcist = require('exorcist');
@@ -163,6 +164,9 @@ module.exports = function createBundle(config, buildOpts) {
     if (transform === 'coffee') {
       bundle.transform(coffeeify);
     }
+    if (transform === 'babel') {
+      bundle.transform(babelify);
+    }
   });
 
   if (config.minify) {