Fix using cl functions issue

[syohex]

eval-when-compile for cl.el is not necessary because this package uses
cl.el functions. And switch from cl.el to cl-lib.el, because loading cl.el
at runtime causes byte-compile warning and using cl-lib.el is better than
using cl.el.

[ghost]

Just a heads up that recent Emacs warns requiring cl at runtime.

(require 'cl-lib) and changing them to the prefixed cl-gensym, cl-remove-if, ... might be a better approach. It may also need cl-lib 0.5 as a listed dependency to accommodate old Emacs versions.

[syohex]

Thanks for comment. I have updated.

[dbrock]

Looks good, thanks!