add capsule model/controller, abstraction above lecture
add CRUD for capsule

Would have used the name "Module," but Rails prevents that...
add problemset model & controller
add capsule dependencies
add parent id attributes
link each course to course index
continue capsule work
finish basic CRUD for capsules
add some CRUD for lectures & psets
add DS_STORE to gitignore
check dependencies
Merge branch 'course_capsule' into courses

Conflicts:
	app/controllers/application_controller.rb
	db/schema.rb