Details * Fixes #68 (nesquena/rabl issues tracker) * Message Pack: http://www.msgpack.org/ * Defaults to using the Ruby msgpack gem: http://rubygems.org/gems/msgpack * Adds Rabl configuration option `include_msgpack_root` which has same semantics as include_json_root. * Adds Rabl configuration option `msgpack_engine` which has similar semantics as json_engine. * Adds whole test suite that is essentially a clone of engine_test.rb, but with proper msgpack expected values. Note that I converted the JSON expected values to their msgpack equivalent in this process. * Updated README.md to reflect the msgpack changes.