Bump riakc dep to 3038f3bcc23dd3b759c0f1124dab6ab4b8f3a9e0

Bump riakc dependency to 3038f3bcc23dd3b759c0f1124dab6ab4b8f3a9e0
in order to pull in the 2.0.0.16 tag of riak_pb.
Merge pull request #46 from basho/feature/riakc-commit-bump

Bump riakc dep to 3038f3bcc23dd3b759c0f1124dab6ab4b8f3a9e0