change time format in submissions
submissions filtered by tutor
Added the skeleton to implement materials.
Sorry, syntax errors while reformatting.
This migration really works now.

Conflicts:
	db/schema.rb
Properly compute the number of new materials uploaded. Also make sure that the materials have the last update/create timestamps stored (like a normal filesystem)
Only return the top-level materials folders when enumerating the folders belonging to a course.
Simplify the design a little; allow only one root folder per course.
Handle the situation where a course does not have any folders or materials defined.
Basic templates for folder listings. Doesn't actually list, for now.
Show and index for the materials controller should give a folder listing.
I can get away with 1 controller and 1 view for materials folder listings.
Fix listing different subfolders with IDs.
Fix new material route.
Yay, I got the nav bar to work.
At every folder listing, we can upload a file or we can create a subfolder.
Change Materials page to match Mission page.
Follow RESTful principles: index will show a listing, show will get the actual material.
Implemented listing subfolders.
Implemented full display of folder contents.