Add support for opening existing tiles
add tile-info.py
ZIgzag and delta decoding
change VectorTile.to_geojson to return a dict, not a string
remove extra ,
some basic tests, that don't pass
make indentation of _handle_attr  match the rest of file
return false when a point is not added
better coordinates in test_key_value_deduplication
incorporate tests from https://github.com/mapbox/mapnik-vector-tile/blob/master/test/python/test.py
Add more complete test for tile creation
Merge pull request #2 from JesseCrocker/master

Add support for decoding existing tiles