Add headers/footers for package.el compatibility

Hi Christophe -- these changes would allow MELPA to package iplayer.el.

The Version header is not technically required for MELPA (since we insert our own snapshot version) but is generally required by package.el.

I used the standard elisp template which applies the GPL -- I'm happy to remove or replace it if you prefer.

Ideally, one would provide at least one autoloaded function so that users don't need to explicitly require the lib after installing it: I might prepare an additional pull request for that.

Cheers,

-Steve