Rubinius no longer supports language mode (mode18, mode19), now test project against last major 2 release
Update to Rubinius 2.2.1

 - Set Travis config rbx version to 2.2.1 (tested locally)
 - Update HTTParty (previous version required deprecated iconv support)
 - Add rbx-specfic loading of ruby stdlib
Remove 1.9.2 support

HTTParty 0.12 requires at least Ruby 1.9.3 and we require HTTParty
0.12 for Rubinius 2.x functionality.

 - Remove MRI 1.9.2 from travis-ci tests
 - Explicitly set the minimum Ruby version in gemspec
Merge pull request #7 from senseobservationsystems/rbx-travis-update

Rbx travis update