Add an endpoint for creating a new friend

[#22]
Actually call _super() correctly in friends route

I was calling super(), but not passing the arguments, which meant that
the model in the friends route was always null. #whoops

[#22]
Make the + button ask the API to create a new friend

[#22]
Clear out all the data on logout
Now we shouldn't have to worry about spooky crufty data anymore.

[#22]