Merge branch 'assignment-4'
Let students create an attendance
Add failing feature spec for student seating

The student index page will now show students either sitting in one of
the four quadrants or as absent.
Render students based on their attendance
Use present to define in_seat
Validate only one attendance per student per day
Set attendance attended_on in controller
Add numericality seat validations
Add some styling for present students
Clarify wording in spec
Fix spec failures after crazy rebase
Configure timezone
Merge branch 'assignment-5'