Added test for queue having no messages on it when created and create
enough code to make it compile
Made 'queueShouldHaveNoMessagesOnItWhenCreated' test pass by returning 0
in the InstructionQueue getNumberOfMessages() method
Added a failing test for queue having a size of one when a message is
added to it and added code to get the test to compile
Added test for the InstructionMessage having an InstructionType that can
be accessed and boilerplate code around that