Correct return types in dummy implementation class

Author: hannesvdvreken

src/Dummy.php

@@ -7,6 +7,8 @@ class Dummy implements TwilioInterface
      * @param string $to
      * @param string $message
      * @param string $from
+     *
+     * @return \Services_Twilio_Rest_Call|void
      */
     public function message($to, $message, $from = null)
     {
@@ -17,6 +19,8 @@ public function message($to, $message, $from = null)
      * @param string $message
      * @param array $mediaUrls
      * @param string $from
+     *
+     * @return \Services_Twilio_Rest_Call|void
      */
     public function messageWithMedia($to, $message, array $mediaUrls = null, $from = null)
     {
@@ -27,6 +31,8 @@ public function messageWithMedia($to, $message, array $mediaUrls = null, $from =
      * @param string|callable $message
      * @param array $options
      * @param string $from
+     *
+     * @return \Services_Twilio_Rest_Call|void
      */
     public function call($to, $message, array $options = [], $from = null)
     {