Return :unauthorized when the user can't create a room, refs #809

Was setting an error flash but returning 200.
Bump to version 1.3.0
Use 'bundle exec' for all commands in the Rakefile
Add 'therubyracer' to the bundle

Necessary when running 'bundle install'.
Fixed half of the failing integration tests

Calls to bbbot-ruby and other things were making most of the tests fail. This
general problems were fixed, but some of the features are failing.

Updated capybara and related gems to their latest versions.
Reverting capybara's version so the gem works with ruby 1.9.2

Capybara 2.1 requires ruby 1.9.3. The gem should still work with 1.9.2 for now.
Modify empty json responses to prevent errors with jquery

When using 'head :ok' to respond with a json, the body is sent as ' ' (an empty
space). This is interpreted by jquery as an error even if the response code is 200.
The way we're doing it now sends a string in the body and is interpreted as a
successful response. See more about it at:
* http://stackoverflow.com/questions/12407328/rails-head-ok-interpreted-as-ajaxerror
* https://github.com/rails/rails/issues/1742