Update eslint-plugin-react and enforce usage of <> for fragments

[BPScott]

See https://github.com/yannickcr/eslint-plugin-react/blob/master/docs/rules/jsx-fragments.md

[GoodForOneFare]

Looks 7.12 added a bunch of new rules. Can we at least raise an issue to figure out our defaults for these?

Ideally, this PR would add them all, though :)

[BPScott]

Looks 7.12 added a bunch of new rules. Can we at least raise an issue to figure out our defaults for these?

jsx-fragments is the only new rule. The rest of the Added section is adding new functionality to existing rules rather than adding entirely new rules. lib/config/rules/react.js already contains defaults for no-typos, jsx-indent and jsx-no-literals, the same goes for every rule mentioned in the fixed block.

[GoodForOneFare]

Cool, so long as someone vetted those changes 🚢