Fix BatchType enum values
Default to protocol version 2
Switch from class-level params to init args
Encode params but don't bind for batch statements
Pass protocol version to MessageType.send_body()
Handle unbound params in v2 protocol QueryMessage
Fix BatchMessage sub-query type checking
Basic integration test for BatchStatements
Switch integration tests to 2.0.5 for now
Correctly clear ccm after changing C* version