Support Travis Ruby version aliases [WIP]

The spec fails, but it looks like there might a bug in JRuby, RVM or a mis-assumption by Travis:

```
rvm use jruby-d20
ruby --version # => "jruby 1.7.4 (1.9.3p392)"
```

Using `jruby-d20` does not ensure 2.0.0 syntax. This happens locally on MacOS and the same happens on Linux as can be seen in this Travis job: https://travis-ci.org/krisleech/chalk_dust/jobs/11102602