Minor code refactor

[glnygl]

Hi James,

Congratulations for this cool framework. Here is my little suggestion about truncate func. I think instead of using Swift.min you can easily do it with simple array code just like below.

---

mutating func truncate(to index: Int) {
    guard index < self.count && index >= 0 else {
        return
    }
    self = Array(self[..<Swift.min(index + 1, self.count)])
}

---

mutating func truncate(to index: Int)  {
    guard index < self.count && index >= 0 else {
        return
    }
    self =  Array(self[0...index])
}

Enjoy coding 🍎