Build out dashboard

:fork_and_knife: Building out the new Dashboard UI based on [this wireframe](https://projects.invisionapp.com/share/DJTGYMX7#/screens). This also adds the implementation for a _very basic_ cookbook activity feed. The activity feed will currently only show you cookbook version updates for the cookbooks you follow. This will undoubtedly will become more robust once we determine all of the use cases for the cookbook activity feed but this approach should do for now :smile:

Both the "You're Following X Cookbooks" and "View All of Your Cookbooks" links go nowhere as those features aren't built out yet but I added the hardcoded class to both of them so we remember to link them up.

I wrote a bit of copy for the no cookbooks data view, it's pretty high level but it should do.