Try to load hammer.js from window before loading via require()

lib/module/hammer.js

@@ -1,7 +1,8 @@
 // Only load hammer.js when in a browser environment
 // (loading hammer.js in a node.js environment gives errors)
 if (typeof window !== 'undefined') {
-  module.exports = require('hammerjs');
+  module.exports = window['Hammer'] || require('hammerjs');
+  // TODO: throw an error when hammerjs is not available?
 }
 else {
   module.exports = function () {