- Extracts the poll interval in riak_poller.rb to a constant and sets it
  to 3 seconds.  The idea is to ensure that the list keys operation will
complete before the next poll begins.
- Adds the clear-cluster.sh script to SSH across the cluster to stop
  Riak, remove all data, and restart Riak
- Adds a default SSH public/private key (config/files/id_riak_rsa) for
  password-less SSH authentication
- Modifies the Vagrant configuration scripts to push the SSH keys into
  the driver VM