Revert "GeoJSON should not be forced WGS84."
Revert "GeoJSON should not be forced WGS84."

This change would break any existing projects that use GeoJSON. So it
needs more thought.

This reverts commit 42180119a2c2d1bfca188ae7a3774526035e4685.

mapbox/millstone,CartoDB/millstone,BHare1985/millstone