Install a `pyzmq` package compiled against `libzmq3`. Fixes #57.

Although Debian experimental has `libzmq3`, it does not have `pyzmq` compiled against it. We install `pyzmq` from `pip` having `libzmq3` already installed.
Install pyzmq from pip after salt being installed. Override current pyzmq.
No user input using apt.
Warn Debian users about installing PyZMQ from PyPi.
Only add Debian experimental repository if not yet added.
Because of PyZMQ need to be compiled against ZMQ3, add the pip allowed checks.
Add test suite dependencies install commands for Debian based distributions.
Merge branch 'develop' into issues/57
Update the tests to work with and around the extra `-P` flag.
`sudo` should not be provided.
Another `sudo` "bytes" the dust.
Stop any apt interaction. Pip install pyzmq after Debian's package has been installed so we override it.
Skip syndic install test case since it's a know failure until Debian packages are >=0.13
Merge branch 'develop' of github.com:saltstack/salt-bootstrap into issues/57
Merge branch 'develop' of github.com:saltstack/salt-bootstrap into issues/57
Merge branch 'develop' of github.com:saltstack/salt-bootstrap into issues/57
Merge branch 'develop' of github.com:saltstack/salt-bootstrap into issues/57
Merge pull request #59 from s0undt3ch/issues/57

Install a `pyzmq` package compiled against `libzmq3`. Fixes #57.
Add `python-pip` as a package dep. It was missing.