Use Carton to create ELPA package.

No longer requires package-build.el from
https://github.com/milkypostman/melpa.

Now requires Carton from https://github.com/rejeep/carton instead.
Explicitly use bsdtar as tar command.

It is available on both my mac and my ubuntu.
Added --atx-headers to README generation again.

Produces a nicer README for marmalade-repo.org that way.
Added an auto complete insert action.

If `php-extras-auto-complete-insert-parenthesis` is t insert a pair of
parenthesis after the inserted auto complete selection; place point in
between the parenthesis and show the `eldoc` documentation for the
inserted selection.
Bumped version number to 0.4.0.
Merge branch 'release/0.4.0'