COSMIT pep8
FIX: variable naming inconsistency in NMF
ENH: precompute X_argsorted when possible
DOC: X_argsorted
Flake8
P3K use six to have a python 2 & 3 compatible code base
P3K StringIO vs BytesIO
DOC fix failing doctest due to unicode_literals
Cosmit: more explicit xlabel.
Cosmit: more explicit label.
ENH: use isinstance instead
DOC whitespace in doctest
BUG revert P3K changes that broke mldata tests
rm gender classification example

Accidentally committed in 1967a0b3236ab65e6a18d402753d344860d85b9c.
Removed the use of StringIO, using pickle.dumps instead.