style: add comments to the public methods and members in the root package.

order.go

@@ -6,6 +6,7 @@ package sointu
 // necessary amount when a new item is added, filling the unused slots with -1s.
 type Order []int
 
+// Get returns the value at index; or -1 is the index is out of range
 func (s Order) Get(index int) int {
 	if index < 0 || index >= len(s) {
 		return -1
@@ -13,6 +14,7 @@ func (s Order) Get(index int) int {
 	return s[index]
 }
 
+// Set sets the value at index; appending -1s until the slice is long enough.
 func (s *Order) Set(index, value int) {
 	for len(*s) <= index {
 		*s = append(*s, -1)