chance variable matters now

[nealey]

I guessed at what chance was supposed to do: we now pick a number between 0 and 100 every time through the loop (1 second), and if the number is less than chance, you get a strike.

[nealey]

I found a gist that demonstrates chance in use, so I've updated the code.

Now it chooses a random integer between [0,chance), and if it's zero, you get a strike. This frequency is way more gratifying when you first upload it :)