Don't use formatting on bytes

Formatting bytes works on Py2.x, but breaks in Py3.x, this should resolve the issues but further unit tests will be need to capture any regressions. Formatting will be supported in Py3.5, but generally it'll be better to avoid formatting where it isn't really needed. Resolves #6

ts3/protocol.py

@@ -126,7 +126,7 @@ class TS3Proto():
         self.logger.debug("send_command - %s" % commandstr)
 
         with self.io_lock:
-            self._telnet.write(b"%s\n\r" % commandstr.encode('utf-8'))
+            self._telnet.write(commandstr.encode('utf-8') + b"\n\r")
 
             data = ''
             response = self._telnet.read_until(b"\n\r", self._timeout)