Merge pull request #728 from satra/fix/f_regression

fix: convert input arrays to float
Made old EllipticEnvelop deprecated class
-renamed to **EllipticEnvelope**
-Examples updated
changed message to *Use EllipticEnvelope instead*
Merge pull request #730 from jaquesgrobler/rename_EllipticEnvelope

Made old EllipticEnvelop deprecated class
corrected Gaussian naive-bayes to correctly computer the class priors
Update examples/neighbors/plot_nearest_centroid.py
Update doc/whats_new.rst
Update doc/whats_new.rst
Removed unneeded numpy.array call in test
Added NearestCentroid to 20 newsgroups example
metric fixed in tests
Merge remote-tracking branch 'origin/nearest_centroids' into nearest_centroids
DOC: timings in cluster comparison example
COSMIT: prettier plot
Fixed broken image link
Merge pull request #733 from jaquesgrobler/master

Fixed broken image link
COSMIT simplify input validation in KMeans
DOC small fixes to NearestCentroid classifier

Point out connection to Rocchio classifier from NLP/IR.
Merge branch 'master' of https://github.com/udi/scikit-learn into udi-master
added prior test
more test cases for naive bayes