Cassandra versions prior 2.0.4 didn't have describe_local_ring method. This fix provides a safe fallback to describe_ring method. Fixes #47.
Now that #47 is fixed, we support all C* 2.0 versions.
Merge pull request #56 from datastax/issue-47

Cassandra versions prior 2.0.4 didn't have describe_local_ring method. T...