Fix building Python integers from size_t values

Use the `n` format specifier instead of `l` to build Python integer or long integer objects from size_t values.
Update distribute_setup.py to 0.6.44
Update stackplot docs for legend capabilities

The docs now state that creation of a proxy artist is the preferred method for
creating legends on stackplots.  This is because stackplot creates
PolyCollection objects which are not supported by the legend
brought backend_qt4.py into pep8 compliance.

Not confident that the change to line 399 is the correct thing to do
here.
brought ../backends/backend_qt4agg.py into pep8 compliance
brought qt4_compat.py into pep8 compliance
minor indentation fix
docstring formatting fix
Catch IOError which is thrown by OS X

This error comes up easily becuase fc-list is a X11 program, which is
missing or misconfigured on OS X.
Merge pull request #2153 from tacaswell/qt4_pep8

Qt4 pep8
Closes 1752. Patch3DCollection can now be empty.

Also improved the Patch3DCollection constructor.
Added labels to images in the gallery

- Right now it's just the filename of the example
- It should perhaps be a string that we define in the example file
  (like in scikits-image / scikits-learn)
Merge pull request #2130 from mdboom/distribute-to-setuptools2

Update distribute_setup.py to 0.6.44
Merge remote-tracking branch 'upstream/v1.3.x'
Sprint: Added new external resources page, link from main and content pages
forward keyword args though table
This commented-out code seems unnecessary.
Merge pull request #2168 from katyhuff/minor_cleanup

This commented-out code seems unnecessary.
On Python 3.3, the __loader__ variable may get set when modules are loaded, so this is ok to override
Merge pull request #2161 from tbekolay/better-gallery

Added labels to images in the gallery [sprint]