This is a breaking change; it's supposed to fix#1. Also, it's a
proposal -- not sure if the benefits outweigh the cost of this.
The example/auth.rs binary is not broken by this, as it doesn't use the
API that changed. The tests have been updated accordingly.
I mainly resolved some circular dependencies that had crept in, and
moved code around. I renamed helper.rs because that was not really an
appropriate name anymore, and moved the delegate code into a new module.