ELPA compatibility

- add Author header
- add URL header
- add Commentary section
- add Comment section
- add footer line

For information about this fix, See following GNU Emacs Manual:

- [Simple-Packages](http://www.gnu.org/software/emacs/manual/html_node/elisp/Simple-Packages.html)
- [Library-Headers](http://www.gnu.org/software/emacs/manual/html_node/elisp/Library-Headers.html)