Implements Multiclass hinge loss

Addresses comments

Removes label_vector as required argument. Tests are failing now

Implements vectorized version, Tests pass

Makes code more in line with version at master

Added labels as required parameter in case of multilable problem

Removes labels as a required argument. It's an optional argument

Adds hinge_loss to METRICS_WITH_LABELS in test_common.py

Removes pyflakes and pep8 warnings

Tries to see if indentation in whats_new.rst is resolved

Changes indentation in whats_new.rst

Fixes pep8 and syntax errors

Fixes indentation; Adds docs for labels parameter

Adds a check in case of absence of labels paramter

Makes code consistent

Fixes pep8. Tests pass now

Fixes indentation

Test to illustrate repeating labels

The calculation can be adjusted for missing labels with labels argument

Removes deprecated pos_label and neg_label parameters

Addresses comments. Renamed variables in tests

Does label encoding in all cases; Modified tests

Fixes the pyflakes warning

Minor fix in docstrings

Adds support for string labels; Adds new labels to test the same

Adds documentations in model_evaluation.rst. Addresses comments

Addresses comments regarding documentation;