Ignore .ruby-version and .ruby-gemset
Lock capybara dependency to < 2.2

* Though capybara-webkit 1.1 works with capybara 2.2, it does not
  implement all new features.
Include stdio.h in IgnoreDebugOutput

* Hopefully this fixes Travis issues.
Remove Rubinius from travis.yml

* Travis hasn't been able to build rbx in ages.