add version.List

list.go

@@ -0,0 +1,19 @@
+package version
+
+// List is a slice of versions that implements sort.Interface.
+type List []*Version
+
+func (list List) Len() int {
+	return len(list)
+}
+
+func (list List) Less(i, j int) bool {
+	return list[i].Less(list[j])
+}
+
+func (list List) Swap(i, j int) {
+	a := list[i]
+	b := list[j]
+	list[i] = b
+	list[j] = a
+}