Disable require.ensure as it's not a standard language feature.

[todo]

longform/example/config/webpack.config.prod.js

Lines 110 to 115 in a08f173

	// TODO: Disable require.ensure as it's not a standard language feature.
	// We are waiting for https://github.com/facebookincubator/create-react-app/issues/2176.
	// { parser: { requireEnsure: false } },
	// First, run the linter.
	// It's important to do this before Babel processes the JS.

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This issue was generated by todo based on a TODO comment in a08f173 when #1 was merged. cc @etchteam.