DOC: make distinction between evaluation and pairwise metrics.
Merge branch 'master' of github.com:scikit-learn/scikit-learn
Revert "trying travis cfg with system-site-packages"

This reverts commit 343f895bdb0e3cb2f5c5452bf705256521fed3ba.
ENH added test, started on cross_val_score
ENH adding SomeScore objects for better (?!) grid search interface.
ENH refactor, taking @GaelVaroquaux's and @ogrisel's suggestions into account
ENH deprecated ``score_func``, introduced ``score`` parameter in GridSearchCV
TST test giving score as string in GridSearchCV
FIX rename ``score`` to ``scoring`` because of the name-clash with the ``score`` function.
FIX two score objects, adjust tests to new interface
ENH remove old interface completely from tests.
DOC fix docstring
ENH working on cross_val_score, trying to simplify unsupervised treatment.
ENH better testing of old an new interface. Still a bit to do for unsupervised grid search, though.
FIX usage of scores for unsupervised algorithms.
ENH use new api in permutation_test_score, don't use old api in testing.
ENH fbeta score working, more tests
DOC-string for AsScorer
ENH renamed ap and auc, added RecallScorrer
DOC narrative docs for scoring functions. Put them next to GridSearchCV. Should they go into metrics?