REFACTOR: The Favcount library needs global variables

This moves the library into our lib folder, and refactored it to more
modern Javascript. I've kept the MIT license at the top of the file.

Doing this allows us to import it as a library in Ember CLI and ditch
yet another global variable.

lib/tasks/javascript.rake

@@ -59,8 +59,6 @@ def dependencies
     }, {
       source: 'spectrum-colorpicker/spectrum.css',
       public: true
-    }, {
-      source: 'favcount/favcount.js'
     }, {
       source: 'handlebars/dist/handlebars.js'
     }, {