Added legacy method for registering formatters back (was removed in 0403b17) to ensure backwards compability.

lib/twine/formatters.rb

@@ -4,6 +4,17 @@ module Twine
 
     class << self
       attr_reader :formatters
+
+      ###
+      # registers a new formatter
+      #
+      # formatter_class - the class of the formatter to register
+      #
+      # returns array of active formatters
+      #
+      def register_formatter formatter_class
+        @formatters << formatter_class.new
+      end
     end
   end
 end