Add ellipsis text-overflow for long usernames

There are a few usernames on the homepage right now where the usernames are cut off. This pull requests provides a workaround by showing them with an ellipsis if necessary.

It might be an option to add a title-tag to the link to be able to read the username without clicking through, e.g. 
    
    <a href="/KlarnaEngineers/" class="mini-user" title="KlarnaEngineers">