deferUpdate calls forceUpdate even after unmount

[claudiopro]

If any of the components exported by react-lineto have a delay set, the component may schedule a call to forceUpdate after the component is unmounted:

react-lineto/src/index.jsx

Lines 54 to 58 in 0a6491b

	// Forced update after delay (MS)
	deferUpdate(delay) {
	clearTimeout(this.t);
	this.t = setTimeout(() => this.forceUpdate(), delay);
	}

Fix is trivial and consists into clearing the timeout in componentWillUnmount(). I'll propose a fix shortly.