Bug fix: ensure shardRegion acts in proxy mode on relevant actor systems

`ShardRegion` proxy mode can be activated either by setting the config properties:
* `akka.cluster.roles`
* and `akka.contrib.cluster.sharding.role` (so that it isn't in the `akka.cluster.roles` list)

or, by ensuring that `Props` are `None` when creating the shard region.

Given that the Docker container sets `akka.cluster.roles` when launching a specific Akka container (e.g. see current [lift/exercise@.service.erb](https://github.com/carlpulley/coreos-vagrant/blob/master/unit-files/lift/exercise%40.service.erb) and [lift/profile@.service.erb](https://github.com/carlpulley/coreos-vagrant/blob/master/unit-files/lift/profile%40.service.erb)), then it is probably easiest to use the `None` method of proxying when we boot the service. This PR provides code for doing this.