MRG: Fix FeatureAgglomeration docs
facecolor/edgecolor are passed arguments to savefig if they
differ from rcParam['figure.facecolor']
From nilearn
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
ENH: Add metric support to neighbors_graph
Replace feature with sample
Remove optional input validation from pairwise_metrics
Merge pull request #3946 from MechCoder/doc_fix

[MRG+1] Fix FeatureAgglomeration docs
FIX bug in fit_params assumed to be an array

Fixes gh-3957.
DOC: make LinearSVR appear in the doc reference
DOC fix/expand Imputer example docs

Fixed formatting of Script output in text introduction.

Added more details to the introduction on use cases for imputing.

Fixes gh-3918.
Minor changes: float conversion and rename rnd into rng
Validation of params passed to neighbors_graphs