Updated Makefile.PL.
Added missing modules to prerequisite list in Makefile.PL.
Added file_extensions method to Attean::API::Parser classes.
Update Attean->get_parser to allow getting parsers by media type or file extension.
Update attean_parse to guess default parser type by filename.
Renamed attean_transcode to attean_parse.
Emit readable error if parsed and serialized types do not match.