Update notification count without page refresh

Currently the module requires that the user refresh the page to see an updated notification count. This functionality is fine for a user who is actively working on the site, however one use case could be that the user has the website on a pinned tab while completing other tasks. In this case the user coming back to the page to check for new notifications wouldn't see an updated count as they might expect.

tl;dr: Initiate ajax callback every thirty seconds to check for new notifications.