clean up metrics ns and allow cleanup-impl to default to no-op
check in ns of example consumers and instrumented versions of wordcount test topology
support passing a map of options to defmetricsconsumer, and add parallelism hint option
support passing initial consumer state as option
produce and consume a count metric in wordcount-metrics test topo
new consumer usage, allows multiple registrations

each consumer is defined as a fn that curries the map for the new consumer. the fn takes the existing conf map, and adds the new consumer to any previously existing consumers
add metric helper fn for setting state to conf
update custom metric API, add example usage with inc-metric
add periodicity as required parameter
helper fn for filtering and plucking values from DataPoints
add and use general with-metrics macro