*
@method randomize()
@returns Array
@short Returns a copy of the array with the elements randomized.
@extra Uses Fisher-Yates algorithm.
@example

[1,2,3,4].randomize()  -> [?,?,?,?]

*
function() {
      var arr = this.concat(), i = arr.length, j, x;
      while(i) {
        j = (math.random() * i) | 0;
        x = arr[--i];
        arr[i] = arr[j];
        arr[j] = x;
      }
      return arr;
    }