able to edit poll questions as a user

[mmezher]

If a user goes to https://www.railsschool.org/polls, they are able to edit all poll questions and publish them. This is a security issue since administrators of the site should be the only ones to be able to edit poll questions.

Bug reproduction steps:

1. log in to rails school
2. go to https://www.railsschool.org/polls/
3. press edit on a poll
4. edit the poll question/answer
5. save and publish

Expected Outcome: Access should be denied to a regular user. Only admins should be able to edit polls.
Actual Outcome: The poll will be published to the site for all users to see.