Treat mc_bytes as a gauge (part 2)
send the basic system metrics in a timely fashion

This should avoid the "negative total memory" problem people see in
their reports after restarting daemons.
Merge pull request #107 from cburroughs/neg_mem_total

send the basic system metrics in a timely fashion
Merge pull request #106 from sflow/master

Treat mc_bytes as a gauge (part 2)