Log Message:
Update to 1.3.1:

2013-05-18 Added support for arbitrary rasterization resolutions to the
           SVG backend. Previously the resolution was hard coded to 72
           dpi. Now the backend class takes a image_dpi argument for
           its constructor, adjusts the image bounding box accordingly
           and forwards a magnification factor to the image renderer.
           The code and results now resemble those of the PDF backend.
           - MW

2013-05-08 Changed behavior of hist when given stacked=True and normed=True.
           Histograms are now stacked first, then the sum is normalized.
           Previously, each histogram was normalized, then they were stacked.

2013-04-25 Changed all instances of:

	   from matplotlib import MatplotlibDeprecationWarning as mplDeprecation
	   to:

	   from cbook import mplDeprecation

	   and removed the import into the matplotlib namespace in __init__.py
	   Thomas Caswell

2013-04-15 Added 'axes.xmargin' and 'axes.ymargin' to rpParams to set default
	   margins on auto-scaleing. - TAC

2013-04-16 Added patheffect support for Line2D objects.  -JJL