pa7/heatmap.js — pull request #125 by xile611 (2014-08-15 08:39:09+00:00)
Title: add xOrigin and yOrigin to config

Default origin of points is top-left, but sometime the origin of point may be top-center or others.
So I add two config options to config of heatmap.

PS,fix a bug of _max in Store