ENH remove _is_1d and _check_1d_array thanks to @GaelVaroquaux
flake8
ENH raise ValueError with row vector if multilabel or multioutput is not supported
ENH being less permissive thanks to @jnothman
DOC add example is_multilabel
ENH handle properly row vector
Flake8
ENH better error message
FIX switch to the new format syntax
ENH prettier error message for _binary_clf_curve with bad input shape
ENH use ravel instead of atleast_1d and squeeze whenever possible
ENH coherently input checking for regression metrics
ENH dryer thanks to @jnothman
TST stronger test for _column_or_1d function
Cosmit
ENH better error message when estimators don't specify their parameters in the signature.
TST use TruncatedSVD in random forest tests

RandomizedPCA sparse matrix support is deprecated (and was only doing
an SVD anyway).
Merge branch 'pr_2002'
COSMIT refactor random forests

Very little subclass-specific stuff left in base classes.

Also fix faulty import in forest tests.
COSMIT refactor forests, part 2

Decouple RandomTreesEmbedding from ForestRegressor.