Fix `respond_to?` calls for Ruby 2.0+

[jcredding]

Assert uses respond_to? calls with it's context classes to see if it needs to call it's parents setups and teardowns. This fails in Ruby 2.0+ because protected methods are no longer "visible" unless you pass true as a second arg to respond_to?.

See: http://tenderlovemaking.com/2012/09/07/protected-methods-and-ruby-2-0.html for more information.