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
Added more examples
Fixed hillshading problems with masked elevation arrays
Supports locale-specified encoding for rcfile.

This commit fixes issue #1317.  The locale for the encoding is obtained from
the Python `locale` module, which can be specified by the `LANG` environment
variable.

This was tested by adding a test rc file encoded in UTF-32-BE, and testing that
it decoded correctly.
Merge pull request #3575 from frutiger/locale_encoded_rcfile

Supports locale-specified encoding for rcfile.
Fixes test to assert instead of print

This commit fixes a test added as part of #3575, which was done to fix #1713.
Merge pull request #3578 from frutiger/fix_test_for_issue_1713

Fixes test to assert instead of print
Added array comparison tests for shaded relief