create shared glyph caches and add to glyph cache map
create shared glyph caches and add to glyph cache map

mattdesl/node-fontnik,mattdesl/node-fontnik,mattdesl/node-fontnik,mapbox/node-fontnik,mapbox/node-fontnik,mapbox/node-fontnik,mattdesl/node-fontnik,mapbox/node-fontnik