Fix Lat/Long resolution issue for Leaflet

The rounding error that was previously corrected in rCharts "dev" branch for NVD3 and MORRIS also applies to Leaflet - it rounds the Lat/Long coordinates for JSON points, so that the points snap to a grid of a couple hundred feet. I edited 2 lines with "digits=13" to correct the problem.

P.S. - this is my first time using GitHub like this, so I'm not sure if this is the proper way to suggest a revision. I apologize if not.  Thanks!