Update news feed selector after GitHub front page refactoring

Changed icon click behavior

Previously an active GitHub tab was focused, or if no one existed, a new one was opened. There was no check for "/" were the actual news feed is shown. Now it only focuses existing GitHub tabs if the page is "/", otherwise a new tab is opened.

- Removed debug logs in production due to Mozilla rules
- Prevent the use of * in strict_min_version due to Firefox 51 changes

Fixed news feed selector to match GitHub's new "subscribe" link

- Fixed tab creation index
- Fixed endless notifications when GitHub is down

Fixed view author tab creation

Added "View author" button in notifications and changed URL permissions