Add title attribute to URLs in statuses (#1755)

Since URLs in statuses are truncated, it would be pleasant to see the
full URL when hovering the URL (like on twitter, yes).

app/assets/javascripts/components/components/status_content.jsx

@@ -44,6 +44,7 @@ const StatusContent = React.createClass({
       } else {
         link.setAttribute('target', '_blank');
         link.setAttribute('rel', 'noopener');
+        link.setAttribute('title', link.href);
       }
     }
   },