Update index.js

Solves the issue of state messing up when parent component calls setState [ref leecade/react-native-swiper#569]

src/index.js

@@ -194,6 +194,7 @@ export default class extends Component {
 
   componentWillReceiveProps (nextProps) {
     if (!nextProps.autoplay && this.autoplayTimer) clearTimeout(this.autoplayTimer)
+    if (nextProps.index === this.props.index) return;
     this.setState(this.initState(nextProps, this.props.index !== nextProps.index))
   }