questions now have a one-to-many relationship with answers
added answer into questions#show view to enable answering
can only answer questions (can't make answers floating in space)
addeded nested resources for answers within questions
added form to post answer to question
Merge branch 'users_answer_questions' of https://github.com/feministy/stack_overflow into users_answer_questions
users cannot answer their own questions, must be logged into answer a question