move ESRI:: fallback test into node-srs

[springmeyer]

For the .prj file of shapefiles currently millstone does an initial parse test and if it fails, then calls the same test again but with a prepended ESRI::. This triggers the underlying c library used (ogr) to try to parse the shapefile .prj wkt as if it were a variant of a known type written by ESRI software that uses a few different terms in the prj text. node-srs should do this double check rather than millstone (https://github.com/mapbox/millstone/blob/master/lib/millstone.js#L381)