Register AttemptLogs for exercise attempts.
Add AttemptLog to Django Admin.
API Endpoint for retrieving AttemptLog data. Dummy code to console.log data in exercises.js
Create first pass Backbone Model for Exercise.
Fix error message in student test response saving.
Update userModel with method to return reasonable estimate of server clock time.
Rename exercise model add init function.
Add exercise log model.
Create RESTful API endpoint for saving attempt logs.
Merge branch 'backbone' of https://github.com/rtibbles/ka-lite into backbone

Conflicts:
	kalite/distributed/static/js/distributed/exercises.js