Add Travis CI

[d33tah]

It's completely for free:

https://travis-ci.org/

The idea is that you'd be getting feedback everytime your build/tests fail on any of the platforms you decide to support. Also, it's a simple way to describe to the users how to actually run your program.

[carlosgprado]

I never used it but I'll take a look into it. Thanks for the tip!

[d33tah]

@carlosgprado: let me know if you run into problems with it, I have some experience.