use dfcreative's gl-heatmap2d version

- from gl-vis/gl-heatmap2d#2

Author: etpinard

package.json

@@ -61,7 +61,7 @@
     "gl-contour2d": "^1.1.2",
     "gl-error2d": "^1.2.1",
     "gl-error3d": "^1.0.0",
-    "gl-heatmap2d": "^1.0.2",
+    "gl-heatmap2d": "git://github.com/gl-vis/gl-heatmap2d.git#04cae767bf14444fe236369011e1c414509ea533",
     "gl-line2d": "^1.4.1",
     "gl-line3d": "^1.1.0",
     "gl-mat4": "^1.1.2",