Add stubs for get/set bucket-type props in transport.
Add stubs for get/set bucket-type props in transport.

GabrielNicolasAvellaneda/riak-python-client,GabrielNicolasAvellaneda/riak-python-client,basho/riak-python-client,bmess/riak-python-client,bmess/riak-python-client,basho/riak-python-client,basho/riak-python-client