Device stubs and exceptions added

lib/Exception/GpioException.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace NoccyLabs\Gpio\Exception;
+
+use NoccyLabs\Gpio\GpioPin;
+
+class GpioException extends \Exception
+{
+    protected $pin;
+
+    public function setPin(GpioPin $pin=null)
+    {
+        $this->pin = $pin;
+    }
+    
+    public function getPin()
+    {
+        return $this->pin;
+    }
+}