[Fix bug 858479] Set cache headers in single event iCal export
Merge pull request #387 from johngian/858479-single-ical-cache

[Fix bug 858479] Set cache headers in single event iCal export
[fix bug 866043] Update tabzilla url.
Merge pull request #389 from glogiotatidis/866043

[fix bug 866043] Update tabzilla url.
[fix bug 852532] Voting system tests.
* Tests for view voting/ vote on a voting/ list votings.
* Added mozillian user in initial data.
* Fixed bug: Users belonging in valid poll groups should be able to vote.
Merge pull request #388 from akatsoulas/852532

[fix bug 852532] Voting system tests.