added travis-ci support, update tox config

travis-ci:
Needs an install, otherwise travis tries rake/requirements.txt
Python 3.3 is the latest, we should test for this.
Previous Python 3 versions are not as important.
The base version, Python 2.6 is important though.
We should check every branch and also pull-requests.
So we just exclude branches were we know we will fail (gh-pages, old).

tox:
Remove pypy (having it in travis should be enough)
Remove 3.1 (old), add 3.3 latest
Not even sure if tox.ini should be in the repo or rather
having a local one (with the versions installed) is better.

Adding travis-ci support was proposed by Sam Doshi.

Signed-off-by: Johannes Dewender <github@JonnyJD.net>
re-add Python 3.2 to travis-ci config

As it turns out, there are some problems that arise with Python 3.2,
but don't arise with Python 3.3 anymore.
Python 3.1 is not in the list of supported versions on travis-ci.

Signed-off-by: Johannes Dewender <github@JonnyJD.net>