Add JSON adapter + tests
Refactor main editor into Backbone app

* All the front-end logic is removed from PHP files except for the JS that kicks it off
  * This will be removed once we AJAX-ify everything; app will kick off and download all the info it needs
* Front-end works completely but does not save
Get and set Ace theme from UI via AJAX
Fix default gulp command to run faster
Delete extra AJAX functions
Fix Zip view classes + background label
Editor theme bugfixes and refactoring
Save Gistpen in editor via AJAX
Defaults should be in model