Add namespace package mpl_toolkits to package meta-data
Fix for false detection of gtk3
Merge pull request #2210 from efiring/namespace

Add namespace package mpl_toolkits to package meta-data
Merge pull request #2217 from AdamHeck/master

Fix false detection of gtk3 bindings during install
Try PySide then PyQt4 for Qt4 examples.
Use the correct connect method for PySide.

This should make the examples work with both PyQt4 and PySide (I can only test the later)
Use the same logic as MPL uses when picking Qt interface.

Thanks to Michael Droettboom (https://github.com/matplotlib/matplotlib/pull/2221#issuecomment-21108901)
Merge pull request #2221 from DanielO/master

Try PySide then PyQt4 for Qt4 examples.
add zorder to streamplot
doc for zorder parameter of streamplot
Merge pull request #2225 from mgoacolou/master

add zorder to streamplot
MAINT moved axhline into it's own module

This is part of the refactoring process. All plots methods should be moved to
their own modules. In this commit, I've started the refactoring by moving the
axhline to its own module, lines, which should contain lines and spans
plotting function.
FIX typo in an import
FIX missing imports
MAINT moved hlines to the _lines module
MAINT moved more plotting functions to _lines.
PEP8 axes._lines was not pep8 compliant
FIX missing imports