Demo/practise app: mvvm, picasso, retrofit, recyclerview, pagination, kotlin etc

todo (for later; not part of this demo target):

• [] handle that case when someone keeps loading hundreds of items in the recycler view
• [] user suggestion on no user match
• [] autocomplete when typing username
• [] ask for a user name on first launch, also provide suggestions for trending users
• [] handle both users and orgs for closed pull request search
• [] offer filter to show both closed and open pull requests