add benchmarks for msgp data responses
add benchmarks for msgp data responses

very similar to the json/fast json ones.
except no bench for listing of metric names, just data responses
because that's all we support.
This helps in validating that msgp encoding is faster.

replay/metrictank,raintank/raintank-metric,raintank/metrictank,raintank/metrictank,raintank/metrictank,replay/metrictank,raintank/raintank-metric,replay/metrictank,raintank/metrictank,raintank/raintank-metric,replay/metrictank