cache method calls as valid methods if seen previously to avoid can()
overhead...

DispatchDeny and DispatchAllow work, but not quite the way I want.
For instance, DispatchDeny Custom will deny to Customer:: methods,
while DispatchAllow Custom will allow Custom::Filter->handler() and
Custom->filter(), but deny Customer:: methods.  I think DistpatchAllow
has the proper behavior, but DispatchDeny may need to be changed.
Input is welcome.

create a / => dispatch_index() mapping

test suite
