Package

PLEASE DO NOT MERGE, see below.

These commits only show the steps to move our current code to a  code layout where we can use proper tools to do testing and everything. Just see the last commit regarding updating Travis, now thanks to the package structure we can just run tests just typing ``nosetests`` :smile: 

I know we want to split things up, but until we do so, I think it would be a good idea, if everyone agrees, to merge this commits (will do so, squashing some commits together).

Just because of this merge the tests inside the unittests subfolders started to run also, so instead of 17 tests we will be running 26.

@jordimas: I didn't move the ``integration-tests`` into ``src/tests``, should those be moved to? what was the reason to keep them outside the ``unittests`` folder?