Refinery::Blog.user_class

This issue was tracked in #286.  I've added a config setting so that existing Rails applications can specify their own user class (generally User, but could be anything).

Only added in 2-0-stable as that's what I use in prod, but happy to take a crack at merging the patch into master as well (still learning the ins and outs of Git, so might take me a little bit to get the hang of it).