Merge branch 'release/0.1.1'
Merge branch 'release/0.1.2'
Merge branch 'release/0.2.0'
Merge branch 'release/0.3.0'
Merge branch 'release/0.3.1'
Merge branch 'release/0.3.2'
Merge branch 'release/0.4.0'
Merge branch 'release/0.4.1'
Merge branch 'release/0.4.2'
Merge branch 'release/0.4.3'
Merge branch 'release/0.4.4'
Allow changing Riak backend

This PR allows changing the Riak backend.  From the looks of it though, you'll only be able to change it once because the sed expression in `riak.sh` won't find bitcask after the first time a cluster is stood up.  That may be ok.  Fixes #21
Allow always setting the storage backend
Fix setting default backend
Merge branch 'jp-riak-backend' of github.com:jplock/docker-riak-1 into jp-riak-backend