setup.py: Remove data_files line with '*.markdown' in it.

I'm not sure but I don't think the data_files argument can take
wildcards. And most likely you don't need this if you have a MANIFEST.in
(which does accept wildcards).

Fixes GH-10.
Merge pull request #11 from msabramo/issue-10

setup.py: Remove data_files line with '*.markdown' in