Front end tests with poltergeist

Submitting this as a conversation starter for issue #149.

It adds poltergeist and capybara to allow testing of the frontend.

I had to do some judo with Faye to get it all running. I'm not very happy with the conditionals on Rails.env that I introduced, so if anyone has better ideas let me know!

Also includes a proof of concept test (spec/features/login_spec.rb). Which tests the login, as well as submitting of a couple of chat messages.