Added Travis yml file to build and status image. 

The README file will need to be updated to have it point to the correct urls.

<pre>
.. image:: https://api.travis-ci.org/tlpinney/GeoGit.png
  :target: https://travis-ci.org/tlpinney/GeoGit
</pre>

I have it running here currently 

https://travis-ci.org/tlpinney/GeoGit

Thanks.