Update README.md
add 110m and 50m natural earth land datasets
update import to add ne 50m/110m land tables
updated earth queries for lower zoom levels
use way_area where possible
Merge pull request #51 from mapzen/quick-optimizations

Quick optimizations
COMMITTED VIA CIRCLECI: tilestache config update
Merge branch 'master' into dev

Conflicts:
	README.md
	data/shp2pgsql.sh