Request website permissions when needed

[carlin-q-scott]

Currently, the extension requests permission for all websites that are supported upon install or update. It would be less scary and confusing if it only requested permission for sites after they've been visited. It could also allow people to disallow interaction with sites that they don't want to be controlled by this extension, such as Youtube possibly.

Technical Details

A button will need to be added to the browser toolbar. That button can change color and notify the user when they're viewing a supported site that hasn't been enabled yet. I'm thinking gray for unsupported site, red for disabled site and blue for enabled site.

The button needs to be clicked to toggle extension permission to, and support for the site. That's a requirement of the permissions API. All of the content_script definitions in manifest.json will need to be moved to another json file and read into a new permission-manager.js script.

[carlin-q-scott]

This addresses concerns in issue #36.