(fix): clear() should be after resize during mount

- if height and width are calculated the background color didn't
  get set on initial render previously, this fixes that

Author: Randall Knutson

src/index.js

@@ -32,11 +32,11 @@ export default class SignatureCanvas extends Component {
 
   componentDidMount () {
     this._ctx = this._canvas.getContext("2d");
-    this.clear();
 
     this._handleMouseEvents();
     this._handleTouchEvents();
     this._resizeCanvas();
+    this.clear()
   }
 
   componentWillUnmount() {