Main python files now don't hardcode prefix

All prefix information comes in from a header in the html req. This
allows the app to set the prefix in redirects and in the html but pushes
all instance specific routing to the nginx layer.
updated ref config with new variables
Updated all templates to use the new root var

meta.root is passed to all templates now
Updated readme with some config help
Merge pull request #11 from bradjc/master

Prefix config info is now in nginx