Provide shortcut methods

[igrep]

• spy().received_method_names: spy().received_messages.map(&:method_name)
• spy().received_arguments: spy().received_messages.map(&:arguments)
• Crispy.received_messages(x): spy(x).received_messages
• Crispy.received_method_names(x): Crispy.spy(x).received_messages.map(&:method_name)
• Crispy.received_arguments(x): Crispy.spy(x).received_messages.map(&:arguments)