Catch invalid/expired request URL

`http://geobin.io/foo/request/bar` should be handled similarly to `http://geobin.io/foo` when invalid/expired. Currently it ends up looking like this:

![screen shot 2014-06-18 at 6 14 12 pm](https://cloud.githubusercontent.com/assets/427322/3322628/0db2cada-f74f-11e3-9196-30081174cfa3.png)