Add account creation.

: #devise
Add habits.

: #feature #ui #test #db
Switch to angular data binding for habits table.

: #angular #test #refactor
Change hard-coded strings to helper method calls for angular paths.

: #refactor #angular
Add X-CSRF-Token to HTTP requests.

If we don't, Rails will log us out after making an AJAX call.

: #bug #ui
Actually create habits when the button is clicked.

Added the server-side create route and controller method, as well as
all the angular glue.

: #angular #test