math: It would be nice if the math.Min and math.Max functions accepted a variadic param

Something like this would be nice:

``` go
func min(nums ...int) int {
  number = nums[0]
  for i := 1; i < len(nums); i++ {
    if (nums[i] < number) {
      number = nums[i]
    }
  }
  return number
}
```
