Bug squashing & a few adjustments

So I noticed that the speed increase & more food needed hints were 'flickering' rather than displaying once & switching off.  So I fixed that.  I also decided to make it so that if the number of dogs missed is more than twice the difficulty, the amount of food required per dog will again increase by 1 (previously had it only increasing once when number of dogs missed equalled the difficulty setting).  To offset this slightly, I made each food pickup add 5 rather than 3.

Let me know what you think of the changes!  :)