put vertex transforms for tile ('model') and map center ('view') back into one operation to avoid floating point precision issues in vertex shader
for special effects, make a separate copy of the vertex position in world coords (w/tile adjusment, but not map center adjustment)
kind of a hack until further researching precision issues
Merge branch 'master' into matrix

Conflicts:
	dist/vector-map.debug.js
	dist/vector-map.debug.js.map
	dist/vector-map.min.js
	vertex.glsl
	vertex.glsl.js