Note: Rack 1.4.1 bug breaks dav4rack usage with root_uri_path

This isn't a dav4rack bug, but rather a current Rack 1.4.1 bug I ran into that breaks Dav4Rack.   

Here's the fix:

https://github.com/NickShaffner/rack/commit/6aa26dd4f3c3c3fcac8fc284a63dcdc4e56ad28d

I've submitted a fix to the rack folks, but until they pick it up, here's a fixed version of Rack that works with dav4rack

https://github.com/NickShaffner/rack
