other way to flush rewrite rules

fixes #2 (hopefully)

Author: pfefferle

mf2-feed.php

@@ -13,8 +13,10 @@
   */
 
 add_action( 'init', array( 'Mf2Feed', 'init' ) );
-register_activation_hook( __FILE__, array( 'Mf2Feed', 'flush_rewrite_rules' ) );
-register_deactivation_hook( __FILE__, array( 'Mf2Feed', 'flush_rewrite_rules' ) );
+
+// flush rewrite rules
+register_activation_hook( __FILE__, 'flush_rewrite_rules' );
+register_deactivation_hook( __FILE__, 'flush_rewrite_rules' );
 
 /**
  * Mf2Feed class
@@ -177,15 +179,6 @@ public static function query_vars( $vars ) {
 		return $vars;
 	}
 
-	/**
-	 * reset rewrite rules
-	 */
-	public static function flush_rewrite_rules() {
-		global $wp_rewrite;
-
-		$wp_rewrite->flush_rules();
-	}
-
 	/**
 	 * Echos autodiscovery links
 	 */