WIP - Add ensemble_ring_changes

Ensemble_ring_changes tests writing a value, expanding the cluster, then
updating and reading that value after ring expansion has completed. It
also creates a bucket using a bucket type with a different n_val from
the default bucket type.  The latter tests basho/riak_kv#1008 and it's
corresponding riak_core PR.
Fixup ensemble_ring_changes

* Add some logging
* Ensure updates work before and after ring expansion
Update ensemble_ring_changes w/ node replace test

Additionally fix cluster expansion and make test deterministically pass.
add force_replace test to ensemble_ring_changes
Merge pull request #673 from basho/ajs/ensemble-ring-changes

Add ensemble_ring_changes