ENH: add PolynomialFeatures preprocessor
address PR2585 comments
import pylab -> import matplotlib.pyplot
TST: fix PolynomialFeatures test error
TST: fix doctests & pep8
DOC: adjust notes in PolynomialFeatures
reorder polynomial features
fix ordering & docs of PolynomialFeatures
TST: remove stray print statement
DOC: typo in kernel formulas
Merge pull request #2608 from jakevdp/master

DOC: typo in kernel formulas
Merge pull request #2585 from jakevdp/polynomial

[MRG] ENH: add PolynomialFeatures preprocessor
FIX verbosity of the mds

Now, the verbose option doesn't need to be strictly equal to 2 to print out
the stress at each iteration.
MAINT: unreachable code removed from BernoulliNB

The deleted code was unreachable. The previous call to check_arrays
ensures that X and y have consistent first dimensions.
BUG SVMlight loader should check whether n_features is big enough

scipy.sparse won't complain when it gets a dimensionality that is
too large, causing crashes in estimators.

Fixes #1630.
MAINT: use stable blas getter API
Merge branch 'master' into NB-test-coverage
MAINT: pep8.
Improved binarize check in _count of BernoulliNB and added test cases.