Add option to use a different web root

[jabbors]

It should be possible to service static content and request under a different web root then the default /.

This would simplify setting up the service behind a nginx or Apache2 proxy under different location, e.g. /pome

[rach]

Thanks for the feedback.. it's a great idea.
I've been quite busy lately but I will try to take allocate some time to improve Pome.