TST Refactor test of sklearn/ensemble/tests/test_forest.py
TST refactor oob score testing
Merge pull request #3182 from arjoly/test-forest

[MRG] Modernizes tests for the forest module
CI: make travis run the doctests
Merge pull request #3189 from ogrisel/travis-doctest

CI: make travis run the doctests
DOC multiclass: OvO needs predict_proba or decision_function

Fixes #3183.
FIX TfidfVectorizer exports idf_ attribute