move 'ajax_refresh' argument to PSGI env

Plack::Middleware do not pass on arguments, only the PSGI env, so to be
compatible with Plack::Middleware we need an alternative to arguments.
I don't know if this is the correct solution but it seems to work.
move 'path' argument to PSGI env

Plack::Middleware do not pass on arguments, only the PSGI env, so to be
compatible with Plack::Middleware we need an alternative to arguments.
I don't know if this is the correct solution but it seems to work.
remove unused argument

As far as I could tell this argument doesn't get used and may have been
a copy-paste from the Cache version.