DOC Remove API from index.rst (it is in api.rst)
ENH We call it `learner` instead of classifier

Classifier might better describe the model.
ENH Parallel nfoldcrossvalidation with jug

I had hesitated whether to put this here. It is very useful (and I have
re-written it a couple of time, but it requires jug
[http://luispedro.org/software/jug] which introduces and extra
dependency. However, putting it in an ext subpackage is a good solution.
ext subpackages can have extra dependencies.
BLD+DOC Mark unstable version
DOC Extensions
ENH Cluster agreement for any sequence
BLD Ignore built directory
ENH Better interface to jug

Uses the new __jug_hash__ hook
DOC Basic documentation on kmeans
DOC Document building procedure
DOC Document ext.jug.nfoldcrossvalidation
ENH Add histogram option to assign_centroids
ENH Run kmeans in parallel using jug
BUG When R=None, use a fixed value

Before, we were getting different tasks everytime jug was called. Not good.
ENH Add normalize option to assign_centroids
BUG Fix case where features are constant for a given label
ENH Add select_best_kmeans function
RFCT Use the name `defaultlearner`
ENH Cluster then classify on histogram

This is used in bag-of-visual words models, for example.
BUG Correct test for 3-arg dot

When doing a cross-product, np.dot returns a 0D-array (i.e., a scalar).
So, the previous test was wrong.