Don't use READ-FROM-STRING to parse URI by default

* api.lisp (read-for-resource): Update docstring.

* common.lisp (read-for-resource): Use
SNOOZE-SAFE-SIMPLE-READ:SAFE-SIMPLE-READ-FROM-STRING.

* package.lisp: New package.

* safe-simple-read.lisp: New file

* snooze-tests.lisp (safe-simple-read-back)
(safe-simple-dont-read-back, safe-simple-read-should-error): New tests

* snooze.asd (:snooze): Depends on PARSE-FLOAT. Add
"safe-simple-read".