Fix #273 work right after dup

See:
http://www.jonathanleighton.com/articles/2011/initialize_clone-initialize_dup-and-initialize_copy-in-ruby/

lib/aasm/aasm.rb

@@ -67,6 +67,11 @@ module AASM
     @aasm[name.to_sym] ||= AASM::InstanceBase.new(self, name.to_sym)
   end
 
+  def initialize_dup(other)
+    @aasm = {}
+    super
+  end
+
 private
 
   # Takes args and a from state and removes the first

spec/spec_helper.rb

@@ -3,6 +3,7 @@ $LOAD_PATH.unshift(File.expand_path(File.join(File.dirname(__FILE__), '..', 'lib
 require 'aasm'
 require 'rspec'
 require 'aasm/rspec'
+require 'pry'
 
 # require 'ruby-debug'; Debugger.settings[:autoeval] = true; debugger; rubys_debugger = 'annoying'
 # require 'ruby-debug/completion'

spec/unit/api_spec.rb

@@ -22,6 +22,26 @@ describe "reading the current state" do
   it "uses the provided method even if persisted" do
     expect(ProvidedAndPersistedState.new.aasm.current_state).to eql :gamma
   end
+
+  context "after dup" do
+    it "uses the persistence storage" do
+      source = PersistedState.create!
+      copy = source.dup
+      copy.save!
+
+      copy.release!
+
+      expect(source.aasm_state).to eql 'alpha'
+      expect(source.aasm.current_state).to eql :alpha
+
+      source2 = PersistedState.find(source.id)
+      expect(source2.reload.aasm_state).to eql 'alpha'
+      expect(source2.aasm.current_state).to eql :alpha
+
+      expect(copy.aasm_state).to eql 'beta'
+      expect(copy.aasm.current_state).to eql :beta
+    end
+  end
 end
 
 describe "writing and persisting the current state" do