modify scope call to prevent deprecation warning in rails master

In rails master, stateflow causes the following deprecation warning:

DEPRECATION WARNING: Using #scope without passing a callable object is deprecated. For example `scope :red, where(color: 'red')` should be changed to `scope :red, -> { where(color: 'red') }`. There are numerous gotchas in the former usage and it makes the implementation more complicated and buggy. (If you prefer, you can just define a class method named `self.red`.). (called from scope at /Users/adam/code/botornot/rails_server/vendor/bundle/ruby/1.9.1/bundler/gems/activerecord-deprecated_finders-fe150f26f009/lib/active_record/deprecated_finders/base.rb:71)

I fixed it.