Updated MRI and JRuby versions.

With the release of MRI 2.2.0 and the impending release of JRuby 9000 it is time to update our Travis targets:

* Added MRI `2.2.0`
* Updated MRI `2.1.2` to `2.1.4`
* Removed `jruby-19mode` (the fuzzy install began pulling `jruby 9.0.0.0-SNAPSHOT`)
* Added `jruby-1.7.18` in place of the broken `jruby-19mode` target