This fixes an issue where the server tabs were not loading
according to the last active tab. This used to load last server
no matter what the last used server is.
Fixes - #416.
This PR adds reply option to notifications of macOS using
`node-mac-notifier` and then post the reply for to the webapp.
It also fixes an issue that even though the app is focused the server that sent
the notification did not focus. And it also adds parsing for mentioning. This also
refactors code for notification.
Fixes: #284, #381.
