What's new: new implementation for trees
Added decision_function support to OneVsRestClassifier and a test, test_ovr_single_label_decision_function, in test_multiclass.py
Updated fixes for #2012.
Strengthened tests for OneVsRestClassifier decision_function
Cleaned up tests, and removed unused multilabel parameter in decision_function_ovr
Inlined extraneous function call from decision_function and added a check that the base estimator has a decision_function attribute
PEP8
FIX Minor stuff in document_classification_20newsgroups output

- The size of the test set should be labeled (test set), not (training
  set).
- The generated figure is so tall that it doesn't fit on a Mac laptop
  screen; shrink it by 20%.
ENH Add filters on newsgroup text

It is easy to overfit on the 20newsgroups dataset, by letting
classifiers learn from metadata that commonly appears in newsgroup
texts, but would be useless for identifying topics outside of this set
of newsgroups in 1993.

For example, many classifiers will tell you that three of the most
informative features are "nntp", "posting", and "host", because the
NNTP-Posting-Host header appears with different frequency in different
groups.

The fetch_20newsgroups function now allows you to ask for any of the
following kinds of text to be removed:

- Newsgroup headers (which contain lots of NNTP metadata that can
  identify the group)
- Signature blocks (which often contain multiple terms that uniquely
  identify the person posting, which in turn identifies the group)
- Quote blocks (which contain people's e-mail addresses and large
  amounts of text from another post in the same newsgroup)

The 20newsgroups classification example takes the "--filtered" flag,
which will remove all of these. This noticeably decreases the accuracy
of all classifiers, leaving room for a better method to improve the
accuracy.
DOC 20news filtering with smaller set and MultinomialNB

BernoulliNB in its present form has a hard time showing the good
features, because it isn't really a linear model (XXX fix this).

A smaller test makes this easier to reproduce for users.
FIX: remove debug message
added pxd to Manifest (to be included in source tarball)
Merge remote-tracking branch 'upstream/master'
PY3 fix string literal syntax error
TST skip Graphviz export docstring in trees

Leaves temp files lying around on Python 3.x.
FIX: remove -funroll-all-loops
FIX: ur strings are not supported in Python 3.3
ENH better error message when estimators don't specify their parameters in the signature.
TST use TruncatedSVD in random forest tests

RandomizedPCA sparse matrix support is deprecated (and was only doing
an SVD anyway).