Add examples and refactor code

Add examples and refactor code

elements/Polygon.js

@@ -0,0 +1,25 @@
+import React, {
+    Component,
+    PropTypes,
+    ART
+} from 'react-native';
+import fillFilter from '../lib/fillFilter';
+import strokeFilter from '../lib/strokeFilter';
+import Path from './Path';
+
+class Polygon extends Component{
+    static displayName = 'Polygon';
+    static propTypes = {
+        points: PropTypes.oneOfType([PropTypes.string, PropTypes.number]).isRequired
+    };
+    render() {
+        let props = this.props;
+        let d = 'M' + props.points.trim().replace(/\s+/g, 'L') + 'z';
+        return <Path
+            {...props}
+            points={null}
+            d={d}
+        />;
+    }
+}
+export default Polygon;