Implement Comments and display in table

Prerequisite: #82 (this PR is based off of that branch, not develop)
Closes: #66 

This PR implements the backend API call to /comments and feeds the results through to the table UI.  I added a unit test for the remote call.  This is the first service that has a single API call but returns data for multiple subsections.  The bastardized use of `NSArray *items` in the RemoteService call is documented to indicate the return type.  This is a good example of where a statically typed language would be best.
Annoying comment: Maybe a UITableViewcell subclass, or a constant?