Corrected copy constructor and assignment operator signatures for the Hero
class. Also, removed Heroes.xml. This should have been removed when I
stopped loading the Heroes texture.
Added a check, so the application window will not close when the
mStateStack is empty, and the previous update() was skipped. This was
occurring when breakpoints were hit. The window would lose focus and skip
the call to update() that would initialize the mStateStack. The application
window would close thinking the update() had left the mStateStack in an
empty state. When in fact update() was never called.
First pass making prevention methods selectable.