chore(project): es6ify source code

* use ES6 import / export
* UTILS: export individual utilities
* TESTS: localize TestHelper includes

BREAKING CHANGE:

* all utilities export independent functions
* library sources got ported to ES6. You must now use
  a ES module bundler such as Browserify + babelify or
  Webpack to consume this library (or parts of it).

lib/features/rules/index.js

@@ -1,7 +1,11 @@
-module.exports = {
+import RulesModule from 'diagram-js/lib/features/rules';
+
+import BpmnRules from './BpmnRules';
+
+export default {
   __depends__: [
-    require('diagram-js/lib/features/rules')
+    RulesModule
   ],
   __init__: [ 'bpmnRules' ],
-  bpmnRules: [ 'type', require('./BpmnRules') ]
+  bpmnRules: [ 'type', BpmnRules ]
 };