`deferUpdate` calls `forceUpdate` even after unmount

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.

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