* Raise error when SparseSeries is passed into roc_curve
* Changed "y_true" in second if block to "y_score"
* Remove code to import pandas and add sparseseries check to 'type_of_target' function. Finally, add 'type_of_target' call to _binary_clf_curve
* Remove pandas import and old comparison in roc_curve.
* Add test for 'type_of_target' function
* Add white space after commas
* Correct other white space issues
* Move type_of_target test into try clause, remove test_precision_recall_curve_pos_label since as multiclass it doesn't make sense
* Add test_precision_recall_curve_pos_label back in and also add test_binary_clf_curve to test new logic in _binary_clf_curve function
* Correct syntax and formatting.
* Remove trailing white space
* Correct validation logic
* Update test_multiclass.py per @jnothman 's request.
* Import SkipTest function.
* Remove extra white space from line 303
MAINT Remove sequence of sequence support from datasets
MAINT Remove return_indicator param
MAINT Remove multilabel-seq test in OVR
MAINT Remove multilable-seq test in check_cv
MAINT Remove multilabel seq test in label_binarizer
TST type_of_target returns "unknown" for multilabel-sequence types
TST _check_targets should raise a ValueError
DOC show multilabel indicator as an example; remove return_indicator param
DOC use consistent lower case y for target
* Fixes bugs related to simply checking type(..) equality
* Refactors metrics and preprocessing
* Invalidates mix of sequences of sequences and label indicators in
metrics
* Invalidates row vectors in metrics
* Fixes bug where single-class target led to incorrect F-score
Roman Yurchak