Merge pull request #13 from PiPHP/rewind-fix

Fixed scrutinizer issue: rewind called on undefined var

src/Interrupt/InterruptWatcher.php

@@ -49,7 +49,7 @@ public function register(InputPinInterface $pin, callable $callback)
             $this->streams[$pinNumber] = $this->fileSystem->open($file, 'r');
             stream_set_blocking($this->streams[$pinNumber], false);
             fread($this->streams[$pinNumber], 1);
-            @rewind($stream);
+            @rewind($this->streams[$pinNumber]);
         }
 
         $this->pins[$pinNumber] = $pin;