Fill!

Much improved fill algorithm. Closes #22.
Fix for terrain wall shadows when rendering using Polygons or WebGL. Possibly fixes #37.
Ignore tiles with infinite elevation when setting token elevations. Allow GM to set the tile elevation in the tile config, which will override the terrain elevation at that point.

Experimental speed-up to vision/lighting/sound rendering when the source is contained in a closed set of walls. Uses the fill algorithm to identify closed polygonal areas, speeding up the clockwise sweep.

Update to geometry lib v0.1.2.