Local unit tests

[Tim Hempel]

Unit tests fail when running them on my local resource, apparently some paths are not well configured. I get the following errorwith test_simple_wrapped.py and test_simple_wrapped.py:

IOError: [Errno 2] No such file or directory: '/examples/files/alanine/alanine.pdb'

Tests run with py.test -v --pyargs adaptivemd --doctest-modules.