Use doubles for LatLng and BoundingBox storage.

This makes the fields protected, so we don't need to use getters and
setters internally, and it removes the 1E6 conversion hack that
proliferated throughout the code.

Right now it breaks path overlays, which don't show latitude correctly.

This could, but probably will not, have some effect upon performance.
Make latitude and longitude public and use them internally
Fix path issue: Points actually did not have sub-1E6 precision
Merge pull request #114 from mapbox/latlng-double

Use doubles for LatLng and BoundingBox storage.