Merge pull request #2500 from ndawe/r2

[MRG] AdaBoostRegressor: fix redundant recalculation of error_vect.max()
Merge pull request #2495 from jaquesgrobler/ENH_coverage_travis

add coverage test for travis
ENH: Call plot twice per class label rather than for every point.
ENH: remove offset calculations
ENH: use memset and memcpy when possible
ENH: make sort an inline nogil function
ENH: make node_reset/split/value gil-free
ENH: use npy_int32 type
Merge pull request #2487 from jaquesgrobler/DOC_speed_up_frontpage

another speedup attempt for index.html:
Cosmit: move log_loss.
pep8/257 fixes
more pep8/257 fixes
ENH: Call plot twice per class label rather than for every point.
Merge branch 'plot_dbscan' of https://github.com/ericjster/scikit-learn into plot_dbscan

Fix formatting to be PEP8.
bug fixes in graph_lasso and moving non-custom log-likelihood definition to specific definition of cost
corrected sign error in _objective
pep8 compliance
Merge pull request #2502 from ericjster/plot_dbscan

ENH: Call plot twice per class label rather than for every point.
MAINT add authors to validation.py and pairwise.py
MAINT: use python setup.py clean in Makefile