Configures Travis CI to pass realtime integration specs.

* Switches to PhantomJS webkit driver for javascript capybara specs.
  * Travis CI has this installed by default.
* Starts private pub server before the main script.
* Runs RSpec command as the main spec script.
* Adds `ruby` language configuration per Travis-CI docs.
* Runs private pub server in the background before travis CI specs.
Skips production gems for travis CI for faster builds.

* Cleans up the .travis.yml file too.