radix.go
func (t *Tree) Minimum() (string, interface{}, bool) {
	n := t.root
	for {
		if n.isLeaf() {
			return n.leaf.key, n.leaf.val, true
		}
		if len(n.edges) > 0 {
			n = n.edges[0].node
		} else {
			break
		}
	}
	return "", nil, false
}
func (t *Tree) Minimum() (string, interface{}, bool) {
	n := t.root
	for {
		if n.isLeaf() {
			return n.leaf.key, n.leaf.val, true
		}
		if len(n.edges) > 0 {
			n = n.edges[0].node
		} else {
			break
		}
	}
	return "", nil, false
}
// Minimum is used to return the minimum value in the tree