Suppress notification if error_reporting() has narrowed

If the error_reporting() setting has narrowed since Airbrake's error
handler was installed, respect the new setting. This also resolves the
issue of errors suppressed with the "@" operator being reported to
Airbrake. (Fixes airbrake#105)

src/ErrorHandler.php

@@ -31,6 +31,13 @@ public function __construct(\Airbrake\Notifier $notifier)
      */
     public function onError($code, $message, $file, $line)
     {
+        // If error_reporting() setting has changed since the ErrorHandler was
+        // installed, respect the new settings. This also respects the
+        // @-operator (issue #105)
+        if ($code !== (error_reporting() & $code)) {
+            return false;
+        }
+
         $this->lastError = [
             'message' => $message,
             'file' => $file,