As a member, I want to "up-vote" a paper, so it rises in rankings.

[WrathfulSpatula]

User	System (Web app)
1. PUT /api/submission/:id/upvote	1.
2.	2. Validate that submission and user exists, and return HTTP 400 if not
3.	3. Check if user has already up-voted this submission, and update only if they have not
4.	4. Return HTTP 200 either way
4. (User has up-voted)	4. (Served request)