Update to mean shit clustering narrative documentation.
Update to docstring of meanshift
docstring of module
Fix typos found by Alexandre
Merge pull request #2768 from robertlayton/meanshiftdoc

MRG: Update to Mean Shift clustering documentation
COSMIT remove unused imports and variables
Minor doc example fix
Merge pull request #2820 from ankit-maverick/issue2819

Minor DecisionTree doc example fix
Merge pull request #2818 from jnothman/flakes

COSMIT remove unused imports and variables
Fixed FS1995 citation.
Merge pull request #2825 from bryan-lunt/master

Fixed FS1995 citation.
MISC plot_rfe_with_cross_validation: better comments

Fixes #2817
DOC: grammar and spelling fixes
Merge pull request #2826 from perimosocordiae/patch-1

DOC: grammar and spelling fixes for label propagation
DOC make loss function in SGD consistent with subgradient. Comment by Martin Jaggi :)
Merge pull request #2827 from amueller/fix_subgradient_equation

MRG DOC make loss function in SGD consistent with subgradient.
Cosmit in SGD doc.
Fixed small typo
Merge pull request #2831 from eltermann/doc-typo

Fixed small typo
Merge pull request #2765 from AlexanderFabisch/validation_curves

[MRG] Validation curves