Use CustomCountBubble to indicate upvote/downvote by the logged in user
Improve AboutSubredditPage

* Use CustomCountBubble for showing number of subscribers/active users
* Add NSFW indicator
* Show is the logged in user subscribed to the subreddit or not
Rename QuickdditManager signedIn property to isSignedIn

isSignedIn also ignore access token value and only depends on refresh
token value
Fix GIF fetched from Imgur API is not animated
Change QuickdditManager::createRedditRequest to accept both GET and POST
Add subscribe and unsubscribe option for subreddit