This commit adds:
- a Vagrantfile to build an ubuntu-based virtual machine including
everything required to test yggdrasil+taktuk
- the basic ssh configuration needed for those tests to succeed. The
password-less ssh key is garbage and should not be used for anything
else.

All the tests work at this point.

regression.sh can fail when the g5k tests are passing, simply because
the main code gets notified of group creation in the wrong order.

This commit change the suite to NAK on exit code errors instead of
outputs to try to fix this problem.

This is a temporary fix at best, we should instead improve the tests so
that the validation is more thorough, and results in crashes when
something wrong happens.

Related to issue #2.

Given the recent changes in the yggdrasil code organization, most of the
tests were broken (bad imports mostly).

This commit fixes the tests so that we can run them against yggdrasil
master.

Due to the new arg parsing and base64 encoding, the tests need to follow
the evolution.

With empty c_wrapper folder to host client and server files.

Use Yggdrasil when it's installed on the computer via PIP.
./regresseion.sh will allow to test the program.

In order to avoid naming conflicts, the main function as been called
runner.