Add logout functionality
Merge pull request #5 from lrakhman/logout

Add logout functionality
added user controller and views
Able to create new challenge from new challenge form
Fails to create challenge with invalid challenger
Merge pull request #6 from lrakhman/new_challenge

New challenge
added user_create form and checkbox"
added create user
resolved conflict
Merge pull request #8 from lrakhman/sessions

Sessions
fixed merge conflicts