ENH CountVectorizer using arrays instead of lists
BUG restore empty vocabulary exc in CountVectorizer
ENH prevent copying of indices in CountVectorizer

... and values as well, if possible.
DOC credit @ephes
Merge pull request #1713 from larsmans/vectorizer-memory-use

ENH CounterVectorizer using arrays instead of lists
FIX MinMaxScaler bug.
COSMIT use callable instead of hasattr
Merge pull request #1727 from amueller/min_max_scaler_fix

FIX MinMaxScaler bug
FIX : fix kfold balance due to int rounding
FIX : test due to KFold change
FIX : better fix of KFold balance
fix doctest
Removed an unnecessary if statement in KFold __iter__ method.
Improved the test that checks the balance of sizes of folds returned by KFold.
DOC Corrected the docstring of KFold about the sizes of the folds.
TST : improve test_kfold_balance test
update what's new