New CLI -  riak-admin handoff limit

 * Flag `--node` will operate on the given node
 * Without passing `--node` all nodes operated upon
 * Allow flag `--set N` where N is non-negative integer
 * Allow flag `--show` to show limits
 * `riak-admin handoff` lists subcommmands (limit only for now)
 * `riak-admin handoff limit` shows usage for limit subcommand
 * Add rpc versions of `riak-admin handoff limit --show` when using
   --force-rpc option.
All that said, I think, for now, we're going to leave it in. I've changed the dependency in rebar.config to match the one in Cuttlefish and it works fine. Is there any reason cuttlefish uses such an old version (0.4.3 vs. 0.8.2)? Just inertia?