Added downvotes. restrict users to one vote per comment.

Improved upvoting using client side javascript
Changed professor commenting to show poster's username

Added course and section models
Added courses.ejs and courses routes.

Added form to upload a json file of course data
Fixed example json file
Basic json parsing for course updates
Added new section creation from json
sections now processed in parallel, added course detail view
added course detail view
Merge pull request #4 from eforbes/master

Initial courses/sections additions