Add an option to serve static files from a remote proxy

We use EasyEngine as part of our staging server setup and it's been really great! Thanks so much for making it.

I was wondering if you could include a command to allow static assets to be served from a remote domain. This isn't usually an issue for people using ee on a live site, but as part of a staging setup it can reduce the amount of file transfers that need to take place.

It's fairly easy to add into the site's conf file manually, but it would be even better if it could be set when creating a site or after creating a site using a simple command.

For reference, he's how this can be done in vvv using the vv script.

When running that shell script you set a flag of --images, specify the live site's domain, and it writes an nginx redirect to forward any missing images to the live site.

I think it would be fairly straightforward to create an ee command to do the same thing but I don't have any python experience. Is this something you guys would consider adding?