Create a manager to filter turns in election

Fix too the call method turn in get_queryset() VoteManager
Create a turn field in election
Do a linebreak between  fields in model Election
Dio a conditional to save total_attendance
Add turn in list display and list filter
Implement a get_absolute_url to reverse a election
Create a get_votings template tag
Merge pull request #13 from lucassimon/master

Create a turn field in election model