refactor Network class

app/assets/javascripts/network/network.js

@@ -2,8 +2,7 @@
 
 import BranchGraph from './branch_graph';
 
-(function() {
-  this.Network = (function() {
+export default (function() {
   function Network(opts) {
     var vph;
     $("#filter_ref").click(function() {
@@ -17,5 +16,4 @@ import BranchGraph from './branch_graph';
   }
 
   return Network;
-  })();
-}).call(window);
+})();

app/assets/javascripts/network/network_bundle.js

 /* eslint-disable func-names, space-before-function-paren, prefer-arrow-callback, quotes, no-var, vars-on-top, camelcase, comma-dangle, consistent-return, max-len */
-/* global Network */
 /* global ShortcutsNetwork */
 
-require('./network');
+import Network from './network';
 
 (function() {
   $(function() {