errors should go to stderr, vs. stdout

Errors such as: "failure to return reply" and similar should (IMHO) go to stderr vs. stdout.

Currently, these lines are using logf() vs fatalf().

Lines 193 to 195 in 15f42ac

    
           if err := w.WriteMsg(m1); err != nil { 
        
           	logf("failure to return reply %q", err) 
        
           }

IMHO, fatalf()should either be renamed, or a third error type created, and then any errors (even non-fatal ones) should go to stderr.

	if err := w.WriteMsg(m1); err != nil {
	logf("failure to return reply %q", err)
	}