In all `VDirectiveKey` `argument` is lowercased. required for: vuejs/eslint-plugin-vue#95 Tested on version: 2.0.0-beta.2 **Input** ```html <template> <div v-bind:FooBar=""></div> </template> ``` **Output** ```js ... { "type": "VDirectiveKey", "range": [ 21, 34 ], "loc": { "start": { "line": 2, "column": 9 }, "end": { "line": 2, "column": 22 } }, "name": "bind", "argument": "foobar", "modifiers": [], "shorthand": false } ... ```