Internal methods

We discussed this change on [stackoverflow](http://stackoverflow.com/questions/25319716/using-eves-db-layer-without-http).

I would've liked to implement this as a decorator, but I couldn't think of a way to do that while maintaining only one database lookup.

This does not yet have unit tests, but I thought I'd run it by you for your thoughts before doing any more. Any feedback is appreciated, as I'm a noob to open source contribution.
docstring needs updat. see what's been done in post/post_internal. These docstrings will be used in building developer documentation so it's important they explain what the method purpose, nitpicks etc.