#286 Static file error with 404

#286 I added a simple check for file extensions using the `path` module.  Originally a url like `content/uploads/345.jpg`would result in the following event fires from router

```bash
content/uploads/345.jpg
content/uploads
content/
```

ultimately returning the `client.js` to the browser.

With my adjustment

now the execution stack ends with just

```bash
content/uploads/345.jpg
```

and propagates to the static-middleware which returns a 404 

:warning: this might be a naive solution, but it seems to work.