$(el).data() calls break due to camelCase conversion

Currently this migration script fixes only `$.data()` calls, but `$.fn.data` still have the incompatibility with automatic camelCase conversion.
```js
// el: <div data-my-prop=test />
var data = $(el).data();
// data: {myProp: 'test'}
assert(data['my-prop']===test) // works on jQuery v2, fails on v3
```