Added example for 2D-histogram with variable bin size.
Fixed two typos.
MAINT: Remove uses of the WarningManager class.

WarningManager was a workaround for the lack of the with statement
in Python versions < 2.6. As those versions are no longer supported
it can be removed.

Deprecation notes are added to WarningManager and WarningMessage, but
to avoid a cascade of messages in third party apps, no warnings are
raised at this time, that can be done later.

Closes #3519.
Update twodim_base.py
Merge pull request #3520 from charris/replace-warningmanager

Replace use of WarningManager by warnings.catch_warnings and then deprecate it.
Update twodim_base.py
Merge pull request #3531 from fkbreitl/master

Updated documentation for histogram2d() in twodim_base.py according to discussion
Docstring: point to correct equivalent function

np.compress' "See also" pointed to itself instead to equivalent np.extract
BUG: linalg: norm was computing and then ignoring a product
MAINT: linalg: some more clean up in norm: 'nd' was defined but not used
Merge pull request #3539 from WarrenWeckesser/bug-norm-performance

BUG: linalg: norm was computing and then ignoring a product
Update halffloat.c

Corrected preprocessor form.
Repaired my misunderstanding and added np.extract

I overlooked that np.compress and ndarray.compress are different things and wrongly assumed that it was a typo. I corrected that and added np.extract for equivalency for 1-D arrays.
Merge pull request #3538 from michaelaye/patch-1

Docstring: point to correct equivalent function (one word change)
Link cumsum and diff to one another as theyre roughly the inverse of each other
Merge pull request #3546 from nils-werner/cumsum-diff-link

Link cumsum and diff to one another...
Merge pull request #3541 from jeromekelleher/patch-1

BUG: make preprocessor tests consistent in halffloat.c
DOC: use the new scipy-sphinx-theme in the documentation
DOC: update scipy.org doc build Makefile targets
MAINT: ensure the sphinx theme gets included in source tarballs