To reduce the number of metrics in one dir, have
generate-repr-flood.py break up metrics into clusters of 2 letters
separated by dots.
Log before and after times, and log when there is no queue 1x/minute
as a heartbeat.
Added to repr-pickle-sender:

- Log bytes in file (not bytes sent)
- Log # of metrics in file
- Log time taken for the send
- Log metrics/sec and bytes/sec (though this is bytes read, not bytes sent)
Make the queue files have two places to the right of the decimal so
that sorting works better.