Makes more sense to keep the output function with the tile object source.
Make it so that serialisation to PBF happens in only one place.
Consolidate tile parsing functions into the tile class.
Add compression and decompression to tile input and output functions.
Fix bug: actually pass options to gzip stream.
Make gzip level configurable and add a test for it.
Fix bug where compression level was not passed to tile from HTTP server.
Fix bug where compression level zero was not producing plain (uncompressed) tiles. Added test for same.
Merge pull request #56 from MapQuest/gzip_pbf_output

Gzip PBF output