Setting anchor or button attributes on react-button causes type errors

It should be possible to pass standard HTML attributes for buttons or anchors to the Button component. For example <Button type="submit" /> or <Button href="http://example.com" download />.

However both of these example with cause a type error in typescript, like:

TS2322: Type '{ download: true; }' is not assignable to type 'IntrinsicAttributes & IntrinsicClassAttributes<{ foundation?: any; isCo
mponentMounted: boolean; displayName: string; state: RippledComponentState; componentDidMount(): void; componentWillUnmount(): void; ... 20 more ...; refs: { ...; }; }> & Pick
<...> & Partial<...> & Partial<...>'.
  Property 'download' does not exist on type 'IntrinsicAttributes & IntrinsicClassAttributes<{ foundation?: any; isComponentMounted: boolean; displayName: string; state: Rippl
edComponentState; componentDidMount(): void; componentWillUnmount(): void; ... 20 more ...; refs: { ...; }; }> & Pick<...> & Partial<...> & Partial<...>'.

This is due to ButtonProps only extending HTMLAttributes<T>

[moog16]

merged #680. Thanks for fixing!