meteor percent checking

I think this A) looks nicer and B) is more flexible when it's time to add new meteors or simply adjust a few percentages.
Oh, and the chances table was done with
```
chances = {}
for i=1, 100 do
  table.insert(chances, i)
end
-- taken from here-> http://forums.wowace.com/showthread.php?t=16628
for i = 100, 2, -1 do -- backwards
    local r = math.random(i) -- select a random number between 1 and i
    t[i], t[r] = t[r], t[i] -- swap the randomly selected item to position i
end
```
and then I just hard coded the result...