Fix npm image link

Author: cesarandreu

README.md

@@ -47,7 +47,7 @@ $ npm test -- --local
 
 MIT
 
-[npm-image]: https://img.shields.io/npm/v/koa.svg?style=flat-square
+[npm-image]: https://img.shields.io/npm/v/browser-image-size.svg?style=flat-square
 [npm-url]: https://npmjs.org/package/browser-image-size
 [travis-image]: https://img.shields.io/travis/cesarandreu/browser-image-size/master.svg?style=flat-square
 [travis-url]: https://travis-ci.org/cesarandreu/browser-image-size