feat: update mms and dynamic twiml php samples from 5.x to 6.x

Author: stern-shawn

…c-sms/generate-twiml-dynamic-sms.5.x.php …c-sms/generate-twiml-dynamic-sms.6.x.phprest/messages/generate-twiml-dynamic-sms/generate-twiml-dynamic-sms.5.x.php renamed to rest/messages/generate-twiml-dynamic-sms/generate-twiml-dynamic-sms.6.x.php rest/messages/generate-twiml-dynamic-sms/generate-twiml-dynamic-sms.5.x.php renamed to rest/messages/generate-twiml-dynamic-sms/generate-twiml-dynamic-sms.6.x.php

@@ -5,7 +5,7 @@
 use Twilio\TwiML\MessagingResponse;
 
 $response = new MessagingResponse;
-$message = $response->message();
+$message = $response->message("");
 $message->body("The Robots are coming! Head for the hills!");
 $message->media("https://farm8.staticflickr.com/7090/6941316406_80b4d6d50e_z_d.jpg");
 print $response;