Closes #123 - adding messaging that the challenge is closed, when it is closed
Closes #124 - when a category can't be found we now throw a 404 opposed to a 500
Merge pull request #125 from rossbruniges/wrap-up-push

Closes #123 - adding messaging that the challenge is closed, when it is closed
Merge pull request #126 from rossbruniges/category-500s

Closes #124 - when a category can't be found we now throw a 404
Updating playdoh to latest revision - with django 1.4.4