Enable Travis CI

This pull request should enable Travis CI on the Toopher .NET library. I was able to get the Travis CI steps to work on Ubuntu and Mac, so I believe the Mono setup is (mostly) correct.

The only test is currently a simple assertion that `1 == 1`, so we'll need to add actual tests later.

A few notable resources:
* http://about.travis-ci.org/docs/
* http://danlimerick.wordpress.com/2013/02/03/build-your-open-source-net-project-on-travis-ci/
* http://stackoverflow.com/questions/16751772/how-do-i-use-travis-ci-with-c-sharp-or-f