Least possible changes for package.el compatibility

In relation to #12, these are the least changes technically required for distribution as a package via MELPA or Marmalade.

Note, though, that the `package-menu-describe-package` function allows users to read plain-text info about a package before installing it: this info is extracted from source code via the standard `;;; Commentary:` header section, so without that header no such info can be presented.

In general, following the standard template inserted by `auto-insert-mode` in new elisp files is a good way to ensure compatibility.

-Steve