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
ENH multilabel metrics: accuracy, Hamming, 0-1 loss
BUG broke the what's new while rebasing
TST : improve again  test_kfold_balance test
Merge pull request #1726 from agramfort/round_kfold

MRG : fix kfold balance due to int rounding
DOC FIX foating point issue