Adjusted build_mesos to build 0.20 style python debs

Closes #7 

With this patch I make the new save_python_eggs build debs that are compatible with the new way that mesos python packages are namespaced (mesos.native, mesos.interface)

I'm also building them in a *different* way, using the local files and the setup.py instead of the postinstall egg method. I think this is a good thing and makes the debs more "normal".

Because of the way fpm needs the package names and stuff, I do some special string manipulation to get the right version and package names, determined by the egg given. (should be sustainable as mesos makes more python submodules)


This is due to this bug:
https://github.com/jordansissel/fpm/issues/607#issuecomment-34122239

Hopefully setting it will prevent others from hitting it.