Add sample_weight support to Dummy Regressor
Use np.average instead of np.mean
OPT: Speed improvements by avoiding repeated calls to check_array
Merge pull request #3811 from MechCoder/fix_repeated_checking

[MRG] Fix repeated calls of check_pairwise and type casting in pairwise_distances_argmin_min
ENH Add cross_val_predict function

This function returns the cross-validated prediction for each element in
the input data (i.e., the prediction that is made when that object is in
the test set).
FIX score precision in doctest
Implements Multiclass Hinge loss
Merge pull request #3779 from arjoly/sw-dummy-regressor

[MRG+1] Add sample_weight support to Dummy Regressor
Update what's new
FIX #3503: use linalg.pinv to better deal with singular input data
Fix using ground truth in silhouette score in document clustering. Closes #3806.
DOC explain SelectorMixin strategy with multiple classes.
Sample weight support for hinge loss
COSMIT: Use searchsorted in weighted_percentile
DOC Add note about sample weights in export_graphviz.
Merge pull request #3829 from amueller/feature_selection_from_model_doc

DOC explain SelectorMixin strategy with multiple classes.
unused variables are redefined later
FeatureUnion example using a heterogeneous datasource.

Uses the 20newsgroups dataset. Extracts & processes the subject-line and body
with separate pipelines and combines them with a FeatureUnion.
DOC RidgeCV more explicit documentation of CV parameter, taken from GridSearchCV.