Fix package

[syohex]

• Fix 'Package-Requires' header position
• Use cl-lib functions instead of cl.el
• Add cl-lib.el dependency
• Don't use free variables

[Rahi374]

Thank you for the fixes.

What advantages are there of using cl-lib rather than cl?

[syohex]

What advantages are there of using cl-lib rather than cl?

• cl.el function causes byte-compile warnings.
• cl-lib is preferable than cl.el for Emacs Lisp coding convention
• cl.el functions and macros are alias of cl-lib.el.