Add an exception interface

lib/Github/Exception/ErrorException.php

@@ -7,7 +7,7 @@
  *
  * @author Joseph Bielawski <stloyd@gmail.com>
  */
-class ErrorException extends \ErrorException
+class ErrorException extends \ErrorException implements ExceptionInterface
 {
 
 }

lib/Github/Exception/ExceptionInterface.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace Github\Exception;
+
+interface ExceptionInterface
+{
+
+}

lib/Github/Exception/InvalidArgumentException.php

@@ -7,7 +7,7 @@
  *
  * @author Joseph Bielawski <stloyd@gmail.com>
  */
-class InvalidArgumentException extends \InvalidArgumentException
+class InvalidArgumentException extends \InvalidArgumentException implements ExceptionInterface
 {
 
 }

lib/Github/Exception/RuntimeException.php

@@ -7,7 +7,7 @@
  *
  * @author Joseph Bielawski <stloyd@gmail.com>
  */
-class RuntimeException extends \RuntimeException
+class RuntimeException extends \RuntimeException implements ExceptionInterface
 {
 
 }