Update rebar.config deps

* added getopt
* added riak_cli

TODO: Set a real tag on riak_cli when appropriate
Use ssh to fetch riak_cli. Mea culpa.
Don't need getopt any more
Fix to use the correct riak_cli branch

"master" doesn't exist anymore. It has been renamed to "develop".
Add transfer_limit config callback to handoff_cli

This ensures that when the limit is reduced processes exceeding the
limit get shut down. Uses already existing functionality in
riak_core_handoff_manager for the shutdown.
Merge pull request #669 from basho/transfer_limit-config-callback

Add transfer_limit config callback to handoff_cli