Build with mono on linux and add travis-ci settings

With these changes we can build pythonnet using travis-ci. Many of the tests fail on linux at the moment, mostly because of winforms problems.

The same setup script can be used to build it as a wheel on windows too, so at some point I'd like to make this new script (setupmono.py) the main setup.py script for all platforms and scrap the old scripts and makefiles.

I've not tested on OS X yet.