Update to handle a 401 from the API

Registeres a global jQuery AJAX error handler that will unset the token and
attempt to authenticate with GitHub again.

Move the `Backbone.history` initialization into the `init` function so that it
will only ever be called once.

Adds an `auth` function that can be called in the AJAX error handler.

Closes #5
Use `this` to be consistent
Fix error with unsupported notification type
Wait until routes are defined to start the history
Merge branch 'tombell-revoked-token-handling'

* tombell-revoked-token-handling:
  Wait until routes are defined to start the history
  Use `this` to be consistent
  Update to handle a 401 from the API
Merge branch 'master' of github.com:bkeepers/github-notifications

* 'master' of github.com:bkeepers/github-notifications:
  Don't update if app is uncached
  update app cache every 60 seconds as well
  Update the location of the starting point of the application
  Update application cache before update
  put manifest on html tag
  don't prefer online version
  Use grunt-manifest to generate app manifest

Conflicts:
	app/js/app.coffee