Add autoload cookie to yas/create-php-snippet

The autoload cookie is necessary so we can run yas/create-php-snippet
without an explicit require.

Signed-off-by: Eric James Michael Ritz <lobbyjones@gmail.com>
Add Package-Requires header for ELPA installations

When installed as a package from an ELPA archive such as Marmalade or
MELPA, this header tells package.el to also install php-mode and
yasnippet, which the library requires.

Signed-off-by: Eric James Michael Ritz <lobbyjones@gmail.com>