Travis CI script

Took quite a few tries to get Travis to build it properly (hate having that many commits for something simple). But it's always useful to know when your build fails. Here's the successful build on my fork repo: 
[![Build Status](https://travis-ci.org/cpp3ds/citra.svg?branch=master)](https://travis-ci.org/cpp3ds/citra)


Also, it may be time to start getting rid of those compiler warnings :laughing: