fix key modifiers detecting

Author: rhyzx

src/directives/public/on.js

@@ -112,7 +112,7 @@ export default {
     // key filter
     var keys = Object.keys(this.modifiers)
       .filter(function (key) {
-        return key !== 'stop' && key !== 'prevent'
+        return key !== 'stop' && key !== 'prevent' && key !== 'self'
       })
     if (keys.length) {
       handler = keyFilter(handler, keys)