Add test for asis put via client interfaces.

Requires:

* basho/riak-erlang-client#102
* basho/riak-erlang-http-client#17
* basho/riak_pb#41 (rebased or merged atop the '1.4' branch)
* basho/riak_kv#546

This verifies that the requested 'asis' PUT client feature for bulk-loading purposes works.