TravisCI config.

It builds on Travis-CI with chi-lange 3.3. Default version of GCC is 4.6. That's why it's not enabled. Maybe I'll find a way to enable 4.7 and 4.8 later.

After you add this and enable the project on http://travis-ci.org you can add a badge to the README.md like this:

[![Build Status](https://travis-ci.org/detunized/clearskies_core.png?branch=master)](https://travis-ci.org/detunized/clearskies_core)

Installing GYP and Ninja is PITA. Had to do it manually.