add docs to Publisher interface noting the expectations for published metrics
add docs to Publisher interface noting the expectations for published metrics

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