Add hooks for direct zendesk integration as a Zendesk App

[winhamwr]

Zendesk has released a new App interface with a fairly clean APi and good hooks in to the UI. Write app code to hook in to Gitzen. http://developer.zendesk.com/documentation/apps/introduction.html

Display the github ticket status on the zendesk ticket sidebar (pulled from Gitzen, so that all github authorization lives there).