Added retry policies for Query and Batch Statements. 

This request adds support for retry policies that can be defined at the cluster level as a default for all subsequent queries or can be assigned to an individual query or batch operation.

Also I added code to catch the issue of a batch operation having more than 65536 statements. This limit is a limit of cassandra and not the library.

I figured we could merge this into the master as it is a light change which adds functionality and doesn't break the API.