Committing WIP before pulling in changes from laravel-develop.

NEW
* Created the SchoolSession model and migration will will be used
  to categorize courses according to which session/year they
  belong in. (i.e. Summer 2013)

CHANGES
* Updated the Course model and migration to reflect the addition
  of the school session attribute.

NOTES
* This is a work-in-progress (WIP) commit, before I attempt to
  pull in changes from the the `develop` branch of Laravel.