added responses to questions and answers

We added "response" functionality which is a stupid way of saying comment. We also had to assign an attribute within erb, but it was to take advantage of "form_for"s (will add inline comment). We still don't have validations or styling of any kind, but that's something we'll revisit when we put up the voting functionality.

We used a single response form while populating hidden fields to use the polymorphic associations.