Applied fixes from StyleCI

Author: freekmurze

src/CallMessage.php

@@ -54,4 +54,4 @@ public function from($from)
 
         return $this;
     }
-}
+}

src/Exceptions/CouldNotSendNotification.php

@@ -24,6 +24,6 @@ public static function serviceRespondedWithAnException($exception)
      */
     public static function invalidMessageObject($class)
     {
-        return new static("Message object class `{$class}` is invalid. It should be either `" . SmsMessage::class . "` or `" . CallMessage::class . "`");
+        return new static("Message object class `{$class}` is invalid. It should be either `".SmsMessage::class.'` or `'.CallMessage::class.'`');
     }
 }

src/SmsMessage.php

@@ -54,4 +54,4 @@ public function from($from)
 
         return $this;
     }
-}
+}