allow additional arguments for be_able_to matcher, this requires Ruby 1.8.7 or higher to use matcher

lib/cancan/matchers.rb

@@ -1,13 +1,13 @@
-Spec::Matchers.define :be_able_to do |action, subject|
+Spec::Matchers.define :be_able_to do |*args|
   match do |model|
-    model.can?(action, subject)
+    model.can?(*args)
   end
 
   failure_message_for_should do |model|
-    "expected to be able to #{action.inspect} #{subject.inspect}"
+    "expected to be able to #{args.map(&:inspect).join(" ")}"
   end
 
   failure_message_for_should_not do |model|
-    "expected not to be able to #{action.inspect} #{subject.inspect}"
+    "expected not to be able to #{args.map(&:inspect).join(" ")}"
   end
 end