Check for valid Campfire credentials instead of crashing.
Check for valid Campfire credentials instead of crashing.

Before, if the provided username or password was invalid, Buffet would
hard crash, and the error message looked a lot like the user had failed
to install Tinder, which was pretty far from the truth. Now Buffet
provides helpful diagnostic output.

Change-Id: I48f54c9f476ac1f63577d6804d4758f84e13f785

causes/buffet,causes/buffet