Ruby 2.0 compatibility fix

In ruby 2.0 protected methods are no longer searched when ```respond_to?``` is invoked with only method name (http://tenderlovemaking.com/2012/09/07/protected-methods-and-ruby-2-0.html).

I've fixed new relic compatibility with ruby 2.0 when using rails 3 by simply setting second argument to ```respond_to?``` as ```true``` so it will search private and **protected** methods.

Fix is backward compatible with ruby 1.9 and ruby 1.8.