Generates the Comment Model and Controller

Updates the schema
Adds the associations amoung the users and proposals
Creates nested resources and therefore nested routes
Proposals show their comments
Bug Fix: Signing out link replaced with just list element
Implements ability to create comments on a proposal
Implements a user's ability to delete their comments
Fixes asset pipeline for javascript handling sign out
Merge pull request #5 from ggw215/comments

Commenting Added