handle InvalidTransition in transition_from matcher

This properly returns false vs raising an AASM::InvalidTransition
error when running specs.

lib/aasm/rspec/transition_from.rb

@@ -2,7 +2,11 @@ RSpec::Matchers.define :transition_from do |from_state|
   match do |obj|
     @state_machine_name ||= :default
     obj.aasm(@state_machine_name).current_state = from_state.to_sym
-    obj.send(@event, *@args) && obj.aasm(@state_machine_name).current_state == @to_state.to_sym
+    begin
+      obj.send(@event, *@args) && obj.aasm(@state_machine_name).current_state == @to_state.to_sym
+    rescue AASM::InvalidTransition
+      false
+    end
   end
 
   chain :on do |state_machine_name|

spec/unit/rspec_matcher_spec.rb

@@ -8,14 +8,17 @@ describe 'state machine' do
     it "works for simple state machines" do
       expect(simple).to transition_from(:initialised).to(:filled_out).on_event(:fill_out)
       expect(simple).to_not transition_from(:initialised).to(:authorised).on_event(:fill_out)
+      expect(simple).to_not transition_from(:authorised).to(:filled_out).on_event(:fill_out)
     end
 
     it "works for multiple state machines" do
       expect(multiple).to transition_from(:standing).to(:walking).on_event(:walk).on(:move)
       expect(multiple).to_not transition_from(:standing).to(:running).on_event(:walk).on(:move)
+      expect(multiple).to_not transition_from(:running).to(:walking).on_event(:walk).on(:move)
 
       expect(multiple).to transition_from(:sleeping).to(:processing).on_event(:start).on(:work)
       expect(multiple).to_not transition_from(:sleeping).to(:sleeping).on_event(:start).on(:work)
+      expect(multiple).to_not transition_from(:processing).to(:sleeping).on_event(:start).on(:work)
     end
   end