Have each bench run be concurrent renders.
Add queue-async dep to package.json
Add complex geojson and use it.
Have travis run bench.
Fix path.
Bypass segfault.
block the main loop less
 - allocating the mapnik.Image only when needed helps shave ms off benchmark
be explicit about png32 and zlib compress faster
png8 is actually fast enough with z=1
Merge branch 'master' of github.com:mapbox/tilelive-overlay into bench-async
should not crash any more
Merge branch 'bench-async'

Conflicts:
	index.js