For SFCs a triple slash directive should be used instead of the react import

[unstubbable]

For a component such as:

// foo.jsx
import * as React from 'react';

export const Foo = () => <div />;

tsc generates this declaration file:

// foo.d.ts
/// <reference types="react" />
export declare const Foo: () => JSX.Element;

Therefore I think we should switch from import 'react'; to /// <reference types="react" /> in the case where no class component is exported.

Depends on RyanCavanaugh/dts-dom#39.