bandwidth metering on streams

humanize bandwidth output

instrument conn.Conn for bandwidth metrics

add poll command for continuous bandwidth reporting

move bandwidth tracking onto multiaddr net connections

another mild refactor of recording locations

address concerns from PR

lower mock nodes in race test due to increased goroutines per connection

core/commands/root.go

@@ -95,6 +95,7 @@ var rootSubcommands = map[string]*cmds.Command{
 	"ping":      PingCmd,
 	"refs":      RefsCmd,
 	"repo":      RepoCmd,
+	"stats":     StatsCmd,
 	"swarm":     SwarmCmd,
 	"update":    UpdateCmd,
 	"version":   VersionCmd,