Updated form docs to reflect functional set state

[jordanpapaleo]

fixes#9703

[jwbay]

This is no longer ES5 code 😯

[jordanpapaleo]

That's how a lot of the examples are already. I just continued the process per the issue.

Sent from my smallest computer On May 22, 2017, at 4:32 PM, jwbay <notifications@github.com> wrote: @jwbay commented on this pull request. In docs/docs/forms.md:

```

It is equivalent to this ES5 code: ```js{2} var partialState = {}; partialState[name] = value; -this.setState(partialState); +this.setState(() => partialState); This is no longer ES5 code 😯 — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub, or mute the thread.

[jordanpapaleo]

Put in PR#9748