[Fix bug 1038055] Fix authentication login_failure() definition.

* Implement error handling.
* Fix login_failure() TypeError triggered by BrowserIDException on BrowserID post().
Merge pull request #1035 from johngian/fix-1038055

[Fix bug 1038055] Fix authentication login_failure() definition.
[bug 1033993] Implement new vouching process in /invite page.
[fix bug 997460] Auto-vouch all attendees of the 2013 Summit.
[fix bug 1034152] Update you're vouched email text.
Merge pull request #1032 from akatsoulas/997460

[fix bug 997460] Auto-vouch all attendees of the 2013 Summit.
Merge pull request #1030 from glogiotatidis/1034152

[bug 1034152] Update you're vouched email text