Restructure error sentence per @alto suggestion

Fix failing spec by adding period
Use upstream version of Proc handling
Fix spacing
Restart travis

lib/aasm/core/transition.rb

@@ -58,7 +58,7 @@ module AASM::Core
         failures << code unless result
         result
       when Proc
-        result = (code.arity == 0 ? record.instance_exec(&code) : record.instance_exec(*args, &code))
+        result = (code.parameters.size == 0 ? record.instance_exec(&code) : record.instance_exec(*args, &code))
         failures << code.source_location.join('#') unless result
         result
       when Array

lib/aasm/errors.rb

@@ -10,11 +10,11 @@ module AASM
     end
 
     def message
-      "Event '#{event_name}' cannot transition from '#{object.aasm(state_machine_name).current_state}'#{reasoning}"
+      "Event '#{event_name}' cannot transition from '#{object.aasm(state_machine_name).current_state}'. #{reasoning}"
     end
 
     def reasoning
-      ". Failed callback(s): #{@failures}." unless failures.empty?
+      "Failed callback(s): #{@failures}." unless failures.empty?
     end
   end
 

spec/unit/transition_spec.rb

@@ -6,7 +6,7 @@ describe 'transitions' do
     process = ProcessWithNewDsl.new
     expect { process.stop! }.to raise_error do |err|
       expect(err.class).to eql(AASM::InvalidTransition)
-      expect(err.message).to eql("Event 'stop' cannot transition from 'sleeping'")
+      expect(err.message).to eql("Event 'stop' cannot transition from 'sleeping'. ")
       expect(err.object).to eql(process)
       expect(err.event_name).to eql(:stop)
     end