Adding rcParams option for axis.labelpad
Updating matplotlibrc.template
Refactored LightSource.shade_rgb into three separate functions
Added support for vertical exag and non-uniform spacing to LightSource
Added new blending modes to LightSource for more realistic rendering
Updated shading example to show new styles and added exmaple DEM from SRTM data
Make the "fraction" kwarg behave as it did before recent LightSource enhancements
Strip whitespace and strict PEP8 compliance
Avoid potential divide by zero in LightSource.hillshade
Fix calculation of aspect for hillshading.
Make clipping work properly for effectively planar surfaces
Added tests for LightSource functionality
Added example of using the custom hillshading on a 3D surface plot
PEP8 fixes
Avoid leaking file descriptors in tests and examples
BUG: 3 fixes for widgets (MultiCrusor, SpanSelector, Slider)
include PySide in qt4agg backend check
BUG : fix list comprehensions over class members

Due to scoping fixes in py3k, list comprehensions over class level
attributes during class definition does not work (see
http://stackoverflow.com/questions/13905741/accessing-class-variables-from-a-list-comprehension-in-the-class-definition).

Superficially Fixes #3436. There seem to be other issues
BUG : fix glaring syntax error
BLD/BUG/DOC : made pytz a required dependency

closes #3423