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.
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)
forward keyword args though table
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]
Closes #1079. Allow iterables for Line3DCollection
Update the coding guidelines wrt to docstrings and MEP10
Merge pull request #2170 from mdboom/overriding_loader_is_ok

overriding "__loader__" is ok
Just a minor comment tweak

Documenting where to add titles to figures in the gallery should we choose to
do that.
Merge pull request #2174 from dmcdougall/comment_tweak

Just a minor comment tweak
Merge pull request #2162 from WeatherGod/mplot3d/empty_patch3dcollection

[SPRINT] Closes #1752. Patch3DCollection can now be empty.
Splitted the axes module into smaller chunks
FIX process_plot_format is not in the axes module anymore
ENH now can run the tests on triangulation without the test runner
Documented the changes
DOC the refactoring of the axes module is now mentionned in the API_changes.rst file
ENH shuffled around some extra methods between Axes and _AxesBase
FIX importing _string_to_bool from the wrong module
added test for table zorder