added test case for symbol with ASCII-8BIT encoding
added test case for symbol with ASCII-8BIT encoding

larskanis/msgpack-ruby,larskanis/msgpack-ruby,ojundt/msgpack-ruby,cosmo0920/msgpack-ruby,kou/msgpack-ruby,kou/msgpack-ruby,cosmo0920/msgpack-ruby,kou/msgpack-ruby,ojundt/msgpack-ruby,larskanis/msgpack-ruby,okkez/msgpack-ruby,okkez/msgpack-ruby,okkez/msgpack-ruby,msgpack/msgpack-ruby,kou/msgpack-ruby,okkez/msgpack-ruby,ojundt/msgpack-ruby,cosmo0920/msgpack-ruby,msgpack/msgpack-ruby,ojundt/msgpack-ruby,cosmo0920/msgpack-ruby,msgpack/msgpack-ruby,larskanis/msgpack-ruby