[WIP] Create the dashboard and welcome controller and views.

:construction_worker: 

Just getting the ball rolling with this, but basically there are some big holes
in the application in regards to the user experience. This aims to fill that
hole by creating a dashboard and a welcome page.

The dashboard is what an authenticated user sees. It displays the activity feed
for the cookbooks they follow and easy to find links for the cookbooks they own
and contribute to.

The welcome page is what a non-authenticated user sees. It introduces them to
what Supermarket is and highlights what they can do on Supermarket.