Fixed dependencies to support JRuby

As we have changed from using less 2.1.0 which used therubyracer/v8 explicitly to less 2.2.0+ which uses commonjs, guard-less will now support jruby via thrubyrhino/rhino.

If we could get a release of this ASAP that would be awesome.

I could also set up a travis build, building against JRuby and MRI easily if you are interested.