adding support for class_weight in fit method
adding warning if passing class_weight through fit
changing warn message, making it Deprecation Warning, and removing negative index for py2.7
MRG: Fix FeatureAgglomeration docs
adding simplefilter for warning
facecolor/edgecolor are passed arguments to savefig if they
differ from rcParam['figure.facecolor']
From nilearn
changing warning test to use assert_raises_message
COSMIT: Make how to use partial_fit render properly
ENH: Use check_X_y in pairwise_distances_argmin
Merge pull request #3962 from MechCoder/check_X_y

[MRG] ENH: Use check_X_y in pairwise_distances_argmin
Merge pull request #3931 from dsullivan7/cwwarn

[MRG+1] raising warning for class_weight in fit method
CLN: Fix typo in comment
Merge pull request #3964 from bwignall/boostdoctypo

CLN: Fix typo in comment
FIX: ward_tree now returns children in the same order for both
structured and unstructured versions

Add test for this in test_hierarchical
Add forgotten newline
Cosmetic change in test
Fixed a bug in RFECV when step != 1
Merge pull request #3824 from nmayorov/rfecv_bugfix

[MRG+1] FIX: Bug in RFECV when step is not 1
Merge pull request #3953 from Titan-C/savefigarg

 Use correct savefig arguments in gen_rst.py
FIX: Raise AttributeError for fit_predict