* Upgrade flow to 0.64
This also enables spread operator on jsx on the flow parser:
```js
<div>{...list}</div>
```
I had no idea it was even a thing.
I had to comment out a flow test that no longer parses, but it's no longer in the flow repo and the comment said that it shouldn't be working anyway so I don't think it's going to be a problem.
* Fix build script
Wei-Wei Wu