Logout button should block until /logout is executed.

[ara4n]

If you press the logout button, you immediately get thrown out of the app... even if the /logout request hasn't actually executed yet (e.g. due to bad connectivity). Therefore if you then kill & relaunch the app, you find yourself still logged in, which is terrifying.

We should block on a spinner or something when you hit logout, so the user knows when it's actually happened.