Fixes bowerstatic urls returning 404s

The latest more.static release is broken and it's my fault.

I didn't actually test at all if the bowerstatic urls would be handled. Naturally, since it wasn't tested they weren't. I was able to fix this in more.static, without having to touch anything else. Though bowerstatic should probably get a better api for this.

The problem occured because the handler in bower_injector_tween raises an exception if the path isn't found. The code assumed that it would return a 404 response instead. I'm not sure what I'm doing now is the right thing to do, but at least it works.