Update koa example to point to someone who knows what they're doing.

Author: glenjamin

README.md

@@ -103,15 +103,7 @@ Use the [hapi-webpack-plugin](https://www.npmjs.com/package/hapi-webpack-plugin)
 
 ### Koa
 
-```js
-var app = koa();
-
-var hotMiddleware = require("webpack-hot-middleware")(compiler);
-app.use(function* (next) {
-  yield hotMiddleware.bind(null, this.request, this.response);
-  yield next;
-});
-```
+Use [koa-webpack-middleware](https://www.npmjs.com/package/koa-webpack-middleware), which wraps this module and makes it work with koa.
 
 ## Troubleshooting