Added additional test to 'acceptable media type' test.
Added resource-creating helper methods.
Added 'validate-accept' processor with tests. Also 'process-get' makes an
attempt to use the optimal content type found by the 'validate-accept'
processor which it installs in the request map at key :optimal-ct. If it is
not found, 'process-get' will call util/optimal-media-type itself.