Updated MRI and JRuby Travis build targets

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` (TravisCI [known issue](https://github.com/travis-ci/travis-ci/issues/3067))
* Added `jruby-1.7.17` in place of the broken `jruby-19mode` target

Now you know why there are two commits! :-)

My first commit set `1.7.18`. I reasoning was the same as yours. Once that test run failed again I did some more Googling. That's when I found the 1.7.17 workaround. It's a very unintuitive issue.