ENH: use setuptools for bdist_wheel command

Enable wheel building by importing setuptools.
DOC a note on shuffling for cross-validation
ENH shuffle option for StratifiedKFold
DOC shuffled StratifiedKFold now in whats_new
BUG: fix doctests
DOC: fix restructured text
FIX MemoryError raising in trees (+test)

I got this wrong all along: Cython functions that don't return Python
objects need an "except" clause to actually propagate exceptions (spotted
by @GaelVaroquaux, @arjoly).

Simplified memory management and unified error messages by safe_realloc.
DOC mention that train_test_split returns a random split
Merge pull request #3133 from kmike/patch-2

Mention that train_test_split returns a random split
Using the 'is' token compares identity; this should not be used for string value comparison.
Merge pull request #3134 from jrouly/string_values

Use == instead of is for string comparison in Affinity Propagation
Update working_with_text_data.rst

A few typos have been corrected.
Merge pull request #3135 from ugurthemaster/patch-1

Update working_with_text_data.rst
Add FAQ to docs.
removed sklearn, removed statsmodel, capitalization in SciPy
Add GPU support (there is none and will probably be none) to faq.
DOC faq formulation
typo
DOC: add PyPy support to FAQ

People ask me this all the time.
DOC typo