Is the purpose mainly just to prevent spam / completely unqualified candidates? Its rather trivial to do the post for anyone with dev experience so I can't imagine its much use to actually gauge their skills
But we didn't need it - it turns out the kind of people that are intrigued enough to apply, and have enough ability to install a few libraries are likely great people.
I checked out the EDITD test and it's a little more involved than Parse's.