Addition of Tag Models and Controller

Created the models and controller for the tag object. Passing this over to @nathanychow so he can add more to the Tag back-end. 

This is a very basic introduction to the tag object. No functionality is expected from these files.

Also, @david-yz-liu let me know if I'm doing this right. It seems weird that I'm merging all these commits into the tagging branch.
Indent the right brace the same as the first position after the preceding left parenthesis.