[fix bug 949080] South migration for twitter usernames.

Remove '@' from the start of twitter usernames.
Merge branch 'gh-788'
[bug 949080] Add missing import in case of error.
[Fix bug 964236] fixed email links and displayed IRC name as “IRC: ____” just as it shows on the full profile
Fix bug 964434 - Add membership pending message to group page

Styled pending status bar just above list of members. Moved “Leave Group” button into the info box where other buttons appear.