Update patch level of ruby

To equal the version of ruby used for Big Maven™
Upgrade ruby-version to latest ruby (2.1.4)

Skip what big Maven is on, and go for the latest, most performant,
securest ruby yet.
Remove backbone from build/vendors

Nothing should be committed to the build/ directory. This being there
was causing an issue when trying to build the gem.

See the discussion in pull request #44:
https://github.com/mavenlink/brainstem-js/pull/44
Merge pull request #44 from mavenlink/update-ruby

Update ruby