Initial support for automatic update

[fabiopelosin]

Still to do:

• The Update Manifest URL needs to be set
• The Developer Identifier needs to be set (see here).
• Set the download url of the extension (no zipped) with an appropriate mime:
  • There was a web service which allowed to set the MIME for the raw GtiHub and for the moment we could use it but, I don't remember the name :-(.

Your-.safariextz-URL must be a valid URL to download the current version of your extension. Be sure your web server has the .safariextz file extension associated with the MIME type application/octet-stream. For more information, see “Putting Your Extension on a Web Server.”

[orta]

Cool, this is a good start I can wrap this up

[fabiopelosin]

:beers: