Add basic logging to file support

This currently logs to a json file with the stream type.  This is slow
and hard on the cpu and memory so we need to swich this over to
something like protobufs for the binary logs but this is just a start.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

supervisor.go

@@ -214,3 +214,17 @@ func (s *Supervisor) getContainerForPid(pid int) (runtime.Container, error) {
 func (s *Supervisor) SendEvent(evt *Event) {
 	s.events <- evt
 }
+
+func (s *Supervisor) log(path string, i *runtime.IO) error {
+	config := &logConfig{
+		BundlePath: path,
+		Stdin:      i.Stdin,
+		Stdout:     i.Stdout,
+		Stderr:     i.Stderr,
+	}
+	// TODO: save logger to call close after its all done
+	if _, err := newLogger(config); err != nil {
+		return err
+	}
+	return nil
+}