Add username as a title for mentions (#1385)

Add a title attribute on mention links for both notifications
and mentions in statuses.

Related to #1350

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

@@ -36,6 +36,7 @@ const StatusContent = React.createClass({
 
       if (mention) {
         link.addEventListener('click', this.onMentionClick.bind(this, mention), false);
+        link.setAttribute('title', mention.get('acct'));
       } else if (link.textContent[0] === '#' || (link.previousSibling && link.previousSibling.textContent && link.previousSibling.textContent[link.previousSibling.textContent.length - 1] === '#')) {
         link.addEventListener('click', this.onHashtagClick.bind(this, link.text), false);
       } else if (media) {

app/assets/javascripts/components/features/notifications/components/notification.jsx

@@ -76,7 +76,7 @@ const Notification = React.createClass({
     const account          = notification.get('account');
     const displayName      = account.get('display_name').length > 0 ? account.get('display_name') : account.get('username');
     const displayNameHTML = { __html: emojify(escapeTextContentForBrowser(displayName)) };
-    const link             = <Permalink className='notification__display-name' style={linkStyle} href={account.get('url')} to={`/accounts/${account.get('id')}`} dangerouslySetInnerHTML={displayNameHTML} />;
+    const link             = <Permalink className='notification__display-name' style={linkStyle} href={account.get('url')} title={account.get('acct')} to={`/accounts/${account.get('id')}`} dangerouslySetInnerHTML={displayNameHTML} />;
 
     switch(notification.get('type')) {
       case 'follow':