Fix travis-ci builds

[turicas]

Currently, @andrebco and I added travis-ci to this repository, but some tests are failing only on travis' virtual machines.
We don't know what exactly is creating these failures, so we need to debug it better and fix the problem to have a properly configured CI server.

[fccoelho]

Nice initiative!

[turicas]

I've downloaded travis-php.box Vagrant image (it says "PHP" but as far as I know, they run Python applications in these boxes), but I can't make it work locally.
The idea is to make the tests run in a local VM (as similiar as possible to that runs on travis-ci.org), fix the problems locally and then commit/push the corrections to GitHub.