Better error handling, but largely untested...

* resting-tests.lisp (test-parse-uri): Better tests.

* resting.lisp (add-direct-superclass-test): Remove.
(ensure-atom): New helper.
(explain-condition): New API function.
(defroute): Much clarified. Horrible argchecker-dummy hack.
(rest-acceptor): Add FALL-THROUGH-P and document.
(parse-uri): Use better RESOURCE-NAME-REGEXP
(arglist-compatible-p): New helper.
(hunchentoot:acceptor-dispatch-request): Bail out early if no
verb.
(hunchentoot:acceptor-dispatch-request): Better error handling.
Tweak README.md
Clean up API a bit

* resting.lisp (rest-acceptor, explain-condition): Move up here.
(convert-arguments): New generic API function.
(:compile-toplevel): Define ADD-DIRECT-SUPERCLASS here.
(check-arguments): New generic internal function.
(define-error): New macro.
(defresource): New macro.
(arglist-compatible-p): Simplify.
(hunchentoot:acceptor-dispatch-request): ROUTE-METHOD -> RESOURCE
Minor test tweak