updates to work with Rails 4.0.2 + Ruby 2.0 on Windows

* bcrypt bumped to ~> 3.1.x (see [this](http://stackoverflow.com/questions/18541062/issues-using-bcrypt-3-0-1-with-ruby2-0-on-windows)), this is also consistent with what ActiveModel 4.0.2 recommends [here](http://api.rubyonrails.org/classes/ActiveModel/SecurePassword/ClassMethods.html)

* updating RedCloth mingw binary as it needs to be cross-compiled with Ruby 2.0. I have submitted a pull request at jgarber/redcloth#18 but until that is merged and a new mingw binary is released, vendoring is the only way for it to "just work"