move legend styling to getCol() from plotMap().

convert Inf to NA in usdyav_est values.
add legend for comparison map. cleanup leaflet initialization.
remove ref to leafletbug_fix.js
close issue#10. get mean lat and lon from geometry of grid.geojson. avoid loading aoi.geojson.
remove aoi.shp to geojson. leaflet no longer depends on aoi to set map view.
a few comments.