Travis CI integration (work in progress)

This PR is just for discussion, please **do not merge** yet.

As of right now the tests are passing for ruby-1.9.3 and ruby-2.1.1, as you can see [on the corresponding Travis page](https://travis-ci.org/olavolav/ai4r).

Rubinius fails because there appears to be [a bug in Marshal#load](https://github.com/rubinius/rubinius/issues/3024) when running Rubinius. I haven't had a chance to look at the other Ruby versions yet.

Do we have an idea what Ruby versions we would like to support?

P.S.: Apologies for all the white space changes, my text editor does this automatically and I guess I didn't pay attention. But trailing is evil anyway. :smile: