have workflow add its methods through a module

this allows another module included later in the model to define
similarly named methods and have them take precedence over (and also be
able to use via super) the ones defined by workflow.

Change-Id: Ib4fb472c1a1fc90e571fb3f006f0eccb29e96fcc
Reviewed-on: https://gerrit.instructure.com/43976
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Jacob Fugal <jacob@instructure.com>
Product-Review: Jacob Fugal <jacob@instructure.com>

gems/workflow/lib/workflow.rb

@@ -112,10 +112,11 @@ module Workflow
     end
  
     def workflow(&specification)
+      workflow_methods = Module.new
       self.workflow_spec = Specification.new(Hash.new, &specification)
       self.workflow_spec.states.values.each do |state|
         state_name = state.name
-        module_eval do
+        workflow_methods.module_eval do
           define_method "#{state_name}?" do
             state_name == current_state.name
           end
@@ -123,7 +124,7 @@ module Workflow
  
         state.events.values.each do |event|
           event_name = event.name
-          module_eval do
+          workflow_methods.module_eval do
             define_method "#{event_name}!".to_sym do |*args|
               process_event!(event_name, *args)
             end
@@ -134,6 +135,8 @@ module Workflow
           end
         end
       end
+
+      include workflow_methods
     end
   end