serial_io: Add confidence output to cmd()

the command should force the user to react to outputs that don't meet the
prompt.

See GitHub Issue #60.

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>

monk_tf/serial_io.py

@@ -91,7 +91,7 @@ def cmd(self, msg, prompt=None, sleep_time=.1, timeout=5, linesep="\n"):
                 sleep_time,
                 timeout
         )
-        return self.last_output
+        return self.last_confidence, self.last_output
 
 
     def read_until(self, end_strip, start_strip=None, sleep_time=.1, timeout=5):