The beginnings of client-side rendering.  The server now looks at the extension requested to determine the format in which it will send back the data, and will send tiles back in JSON format.  As a side issue that was necessary to achieve this, a lot of pyramid types now have the tile file extension passed-in rather than defined by the serializer - eliminating the need for a serializer in cases where one only wants raw data.  As another side note, we have a bug in our AVRO serialization, which we can work around for the moment, but which causes problems if we try to read files properly - they only have one record, but think they have more.  So for now, we always only try to read one, and we're fine.
Merge branch 'master' of github.com:oculusinfo/aperture-tiles