Claylib needs smoke tests

[shelvick]

For now I think the best way of testing is through the examples, but it would be nice to have a couple of functions to run sets of examples at once rather than a bunch of manual REPL forms. Run the more complicated examples (and a different function for all of them) one by one, hit Escape when you're satisfied that it works, and then it runs the next one.

[mjkalyan]

(defmacro run-all-examples ()
  `(progn ,@(mapcar (lambda (example) (loop for s being the external-symbols of example
                                            when (fboundp s) collect (funcall s)))
             (list-system-packages #:claylib/examples)))) ; TODO define list-system-packages

This assumes you don't make functions other than main external.