Restore travis to a working state.

The following pull requests restores travis to a state where globaleaks gets *tested* but **not** *installed* on a travis environment.

There have been tons of attempt, and tons of different commits adding/removing the same stuff. 
I tried to shrink them as much as possible, keeping them meaningful.
If you are willing to review only a smaller subset of commits, I will do my best to squash them to eventually reach an even smaller subset of commits.
i discussed this with @fpietrosanti.

he is convinced that we should consider to use the one provided by the distro. my concern is for ubuntu 12.04 where Tor is really outdated so that it spawn out various warning messages as tor itselfs detect to be outdated.