Added a Message Box class

This is a message box object. Since there's most likely only going to be
one message box, I reserved the variable "message" to be the MessageBox
object. It requires you to provide a rect place the text and message in.
To modify the text just modify the MessageBox's text parameter. Make
sure it only fires once, or it'll update every frame!

Yet to include: text wrapping.

PS, I think I left a game loop in there to test out the button so I'll
remove it on a next update
Added Player class

player class contains the money balance of the player and methods to
increase,  decrease, and get the balance.