DOC: Simpler cross-validation iterator doc
2-fold => 2-fold cross-validation
approximately the same percentage of samples
Remove spurious print statements in sample snippets to make the doc easier to follow
Lowercase y and more consistent blank line usage
DOC: missing documentation of splitter parameter in tree.py
Merge pull request #2385 from ndawe/tree

[MRG] DOC: missing doc of splitter parameter in tree.py
DOC: removed duplicated Python 3 section

Fixes #2383.
DOC: docstring for predict_log_proba was wrong
Typo

Sorry for the noise :s
GBRT checks if ``loss`` is in self.supported_loss
renamed supported_loss to _SUPPORTED_LOSS (constants)
add test for deprecated warning
Merge pull request #2308 from pprett/gbrt-check-supported-loss

GBRT checks if ``loss`` is in self.supported_loss
COSMIT: fix docstrings in affinity_propagation
ENH: add fast_dot function
employ DataConversionWarning
FIX: avoid zero-dvision warnings
FIX: fix test warning
better handling of warning in test
COSMITS