FIX: wrap sklearn algs in modules ending with "_"

For historical reasons we were not wrapping sklearn algs in modules with
names ending with "_". This restriction prevented us from wrapping algs
that we could have wrapped. We lift it now, since it does not seem to
have any bad side effects anymore.
A proper validation would be to really test that we can run the algs.
FIX: cStringIO does not support Unicode

`autogen` was breaking in nodes with Unicode characters in their docstring.
We traced this down to cStringIO, which unlike StringIO does not support
unicode.
Merge pull request #9 from mdp-toolkit/sklearn_debug

Fix a couple of problems with sklearn