Fix docstring of model_locator.ModelData
Use os.path.expanduser() to find homedirectory

This should be more reliable than manually using environment variables.
Add dependencies to numpy and Cython in setup.py

The `install_requires` dependency is important to make sure the target
system fulfills certain requirements independently from whether the
development (and build) system does - even when using binary
distribution.

NOTE: The `setup_requires` dependencies on numpy and Cython are kind of
pointless at the moment, since the modules are imported in the script
beforehand. Still, it seems like good practice to mention those.
Remove distutils as an alternative to setuptools in setup.py

For cpymad setuptools is required anyway since it provides the package
pkg_resources. Allowing distutils only delays the problems.

Setuptools should be available on almost any platform anyways - or at
least easy to install.
Reestablish order when resolving 'extends' for models

Using C3 as resolution order now. Although this is probably overkill,
especially if there are no models with multiple bases, I like to do it
correct from the start. In principle, order matters when merging
dictionaries.

The code is mainly copied from:

http://code.activestate.com/recipes/577748-calculate-the-mro-of-a-class/
Use non version based check for existence of OrderedDict

Version based feature checks are generally unreliable in both
directions.
Use old-style unittest.TestCase.assertRaises for python2.6 support

The python>=2.7 preferred call to this method as a context manager is
not available in python2.6.
Merge pull request #20 from pymad/fix-0722ee8

Looks good to me!

Fix 0722ee8
Merge pull request #21 from pymad/aesthetic-fixes

Aesthetic fixes

I have no problems with any of this, thanks for cleaning!