FIX suspected bug for non-hypercube make_classification
FIX Low-memory cluster sampling in make_classification

This allows larger `n_informative` with small cost, but will not produce
the same output as in previous versions.
FIX don't leave clusters in uint8
Remove debug print statement
FIX update data-dependent test assertion
Use internal sample_with_replacement rather than Python's random.sample
TST/COSMIT cleaner make_classification and fix tests

* refactored make_classification
* new test for make_classification
* skip problematic common test for class_weights
FIX: Ensure expected behaviour when copy=True|False in Imputer
FIX: Don't copy X at imputation in the sparse case
COSMIT: remove useless import
Update docstring + Use np.diff
Update dpgmm.py

The document has been moved.
Update dp-derivation.rst

The subscript has been mislabeled.
The code use this correct formulae, and can be seen in the thesis --Variational Inference for Dirichlet Process Mixtures David Blei, Michael Jordan. Bayesian Analysis, 2006 as well.
DOC Remove target_names from boston dataset object description
Merge pull request #2710 from eshilts/DOC-load_boston

DOC Remove target_names from boston dataset object description
DOC add missing comment for C parameter
DOC remove duplicate reference to example
Merge pull request #2702 from glouppe/imputer-copy

[MRG] Fix #2697 - Copy parameter in Imputer
Merge pull request #2708 from likang7/patch-3

Update dp-derivation.rst
Merge pull request #2706 from likang7/patch-2

Update dpgmm.py