Make it work with static root at /

the check to see if page is static, then use anonymous user is silly for
several reasons.  Performance intensive sites will setup static pages to
be served at the very least by werkzeug, and probably even a couple of
layers above that at nginx or apache, so flask will never see static
requests. The case where it might actually be nice, static requests for
blueprints, isn't even covered.

The check is also quite stupid, since dynamic pages can and do mount
past the static mount point, like in my case where my static mount is /.

Anyway, someone else might find this useful. we need it at Elsevier.