Refactor biome information into biomes.h
Add BiomeOverlay rendermode.

A "biomes" option is specified in rendermodes.py but not yet wired up!
May do unexpected things if used :-)
Add option support to BiomeOverlay()

BiomeOverlay([("Biome", (r,g,b)), ... ])
Add documentation for BiomeOverlay

Have stuck with 'color' as the preferred spelling...
Bump extension version due to new rendermode
Improve default colours for BiomeOverlay
Add support for 'alpha' option and change default
Merge branch 'upstream' into biomesoverlay
Support blockid > 255
Filter out player files not ending in ".dat"
Merge remote-tracking branch 'origin/biomesoverlay' into biomesoverlay
Update to use list comprehensions
Fixed POI infowindow image scaling for FireFox
Fix wood log rotation in lower-left and lower-right orientations.
Merge remote-tracking branches 'tswsl1989/biomesoverlay', 'socolin/patch-2', 'tswsl1989/upstream', 'counterpillow/ffscalefix' and 'maruohon/log-rotation-fix'
updated CONTRIBUTORS.rst

added new contributors, and bumped some long-time contributors to the
"long-term" list.
Add new nether render mode.
c_overviewer is now slightly more binary-compatible across numpy versions
Scrub parens from poi group names

Fixes #814
Clarified docs on overlay option

Closes #789