Avoid manually including Promise everywhere that it is used

ES2015 polyfills have now been centralized in the polyfills.js
script.

.jshintrc

@@ -26,7 +26,6 @@
   "phantom": true,
   "jquery": true,
   "predef": [
-    "-Promise", // We currently support IE10-11 which lack a Promise global
     "angular",
     "assert",
     "after",

h/static/scripts/annotator/anchoring/html.coffee

-Promise = require('core-js/library/es6/promise')
-
 {
   FragmentAnchor
   RangeAnchor

h/static/scripts/annotator/anchoring/pdf.coffee

-Promise = require('core-js/library/es6/promise')
 seek = require('dom-seek')
 
 Annotator = require('annotator')

h/static/scripts/annotator/guest.coffee

-Promise = require('core-js/library/es6/promise')
 baseURI = require('document-base-uri')
 extend = require('extend')
 raf = require('raf')

h/static/scripts/bridge.coffee

-Promise = require('core-js/library/es6/promise')
 extend = require('extend')
 RPC = require('./frame-rpc')
 

h/static/scripts/directive/test/annotation-test.js

 /* jshint node: true */
 'use strict';
 
-var Promise = require('core-js/library/es6/promise');
 var proxyquire = require('proxyquire');
 
 var events = require('../../events');

h/static/scripts/retry-util.js

 'use strict';
 
 var retry = require('retry');
-var Promise = require('core-js/library/es6/promise');
 
 /**
  * Retry a Promise-returning operation until it succeeds or

h/static/scripts/session.js

 'use strict';
 
-var assign = require('core-js/library/fn/object/assign');
 var angular = require('angular');
-var Promise = require('core-js/library/es6/promise');
 
 var events = require('./events');
 var retryUtil = require('./retry-util');
@@ -30,7 +28,7 @@ function sessionActions(options) {
   };
 
   Object.keys(actions).forEach(function (action) {
-    assign(actions[action], options);
+    Object.assign(actions[action], options);
   });
 
   return actions;

h/static/scripts/test/annotation-mapper-test.js

 'use strict';
 
-var Promise = require('core-js/library/es6/promise');
-
 describe('annotationMapper', function() {
   var sandbox = sinon.sandbox.create();
   var $rootScope;

h/static/scripts/test/retry-util-test.js

-var Promise = require('core-js/library/es6/promise');
-
 var retryUtil = require('../retry-util');
 var toResult = require('./promise-util').toResult;