Added code to address issue #1403
In preprocessing.binarize, eliminate zeros from sparse matrices
DOC add narrative overall description of classification metrics
DOC add hinge loss narrative doc
DOC Set reference links in the doc
DOC add narrative doc on zero_one loss metric
DOC add narrative doc on zero_one_score
DOC add narrative doc for precision, recall and fbeta measures
DOC add narrative doc on roc curve
DOC add narrative doc on auc and average precision
DOC add narrative doc on matthews_corrcoef
DOC add narrative doc for explained variance
DOC add reference to multioutput metrics in regression
DOC add link to clustering metrics
Update what's new
ENH renamed metrics.zero_one to metrics.zero_one_loss
ENH rename zero_loss_score to accuracy_score
ENH ClassifierMixin use a metrics from sklearn.metrics
DOC add classification_report to the narrative doc
DOC typo and mistakes