Refactor controllers and helpers

move db actions to models package
refactor helpers
better controller composition
start posts controller
testing to make sure we're actually retrieving the user based on email stored in session. normally if you want something to be available in the template you have to pass it like  `Render(stuff_available_in_template)` but you'll see the functions in `controllers/common.go` accomplish this by adding user to the `RenderArgs`