Add fallback for non Quicklisp systems

file.lisp

@@ -59,8 +59,10 @@
     (clean-or-create (from-quickref-dir "website/"))))
 
 (defun find-readme (release-name)
-  (let ((asd-file (ql-dist:base-directory
-		   (ql-dist:find-release release-name))))
+  (let* ((release (ql-dist:find-release release-name))
+	 (asd-file (if release
+		       (ql-dist:base-directory release)
+		       (asdf:system-source-directory release-name))))
     (car (directory (merge-pathnames "README.*"
 				     asd-file)))))
 (defun file-to-string (pathname)