add support for querying cassandra
add support for querying cassandra

OOM-Killer/metrictank,replay/metrictank,raintank/raintank-metric,replay/metrictank,raintank/metrictank,raintank/raintank-metric,OOM-Killer/metrictank,OOM-Killer/metrictank,raintank/metrictank,replay/metrictank,raintank/raintank-metric,replay/metrictank,raintank/metrictank,raintank/metrictank