Properly passing on horiz-/vertOn to Cursor()

Simple fix to properly pass on the horizOn and vertOn keyword
arguments to the matplotlib.widgets.Cursor constructor.
Make Axes.stem take at least one argument.

When it takes only one, the abscissae default to np.arange(len(y))
Add axes.stem call signature test
Update CHANGELOG with axes.stem change
Improve empty collection check in add_collection.
use QMainWindow.closeEvent for close events

The current code uses the QWidget.destroyed signal
to emit a close event into matplotlib. This is a very
bad idea, as it is a heavy abuse of Qt functionality.

When a main window is closed in Qt, it and its children
are deleted if the DeleteOnClose flag is set (which we
did set). This causes the QWidget.destroyed signal to be
called. Setting the DeleteOnClose flag is a very bad
idea, since objects should only be deleted by the
garbage collector. Soon after, PyQt4 will complain
that "the underlying C++ object has been deleted", since
the object is alive for python but dead for C++.

This patch changes the machinery to use the
QMainWindow.closeEvent to emit a close_event, which is
what one actually wants.
Add test for add_collection
Fix positional argument parsing
Make stem catch explicit Exception classes
Make `rc_context` available via pyplot interface
make rc_context show up in pyplot's docs
BUG: Qt canvas didn't fire resize_event.
adding Ada Lovelace's public domain portrait

Original watercolor portrait by Alfred Edward Chalon, woodcut-style
graphic by Colin Adams for the Ada Initiative, SVG conversion by Fred
the Oyster, and colorization by Kaldari, under CC0 1.0 Universal Public
Domain Dedication, from Wikimedia Commons

http://commons.wikimedia.org/wiki/File:Ada_Lovelace_color.svg
adding Grace Murray Hopper's photo

20 January 1984
Source  U.S. Naval Historical Center Online Library Photograph NH
96919-KN (jpg)
Photographer: James S. Davis

License: All information on this site is in the public domain and may be
distributed or copied unless otherwise specified. Use of appropriate
byline/photo/image credits is requested.

This file is a work of a sailor or employee of the U.S. Navy, taken or
made during the course of the person's official duties. As a work of the
U.S. federal government, the image is in the public domain.

http://en.wikipedia.org/wiki/File:Grace_Hopper.jpg
use Ada Lovelace's and Grace Hopper's images
Document the C/C++ code guidelines
do not convert None labels to 'None'
do not convert None labels to 'None' (now in container.py)
Using a stricter check to see if Python was installed as a framework. Also, because of the recurring problems with non-framework Pythons, importing the Mac OS X backend will now fail (instead of just issuing a warning) if Python is not installed as a framework.
Legend: Also calc the bbox of the legend when the frame is not drawn. This fixes gh1586