Use proper nested example group include statement

.rspec

@@ -1,4 +1,3 @@
 --order random
---color
 --warnings
 -r spec_helper

spec/rspec/support/warnings_spec.rb

@@ -56,10 +56,10 @@
       warning_object.warning 'Message'
     end
 
-    it_should_behave_like 'warning helper', :warning
+    it_behaves_like 'warning helper', :warning
   end
 
   describe "#warn_with message, options" do
-    it_should_behave_like 'warning helper', :warn_with
+    it_behaves_like 'warning helper', :warn_with
   end
 end