initial commit, copy from http://www.fundza.com/algorithmic/quadtree/index.html
add_point() and subdivide()
add_point() and subdivide()
recursive count_overlapping_points()
test large count
refactor feature methods to tests
contains() with shapely polygons
refactor to Feature(geometry=...) to support complex shapes
Merge branch 'master' of https://github.com/ceumicrodata/quadtree