fix golint comments warnings

position/position.go

@@ -6,6 +6,7 @@ import (
 	"github.com/z7zmey/php-parser/node"
 )
 
+// Position represents node position
 type Position struct {
 	StartLine int
 	EndLine   int
@@ -17,8 +18,10 @@ func (p Position) String() string {
 	return fmt.Sprintf("Pos{Line: %d-%d Pos: %d-%d}", p.StartLine, p.EndLine, p.StartPos, p.EndPos)
 }
 
+// Positions a collection of positions attached to nodes
 type Positions map[node.Node]*Position
 
+// AddPosition attaches a position to a node
 func (p Positions) AddPosition(node node.Node, position *Position) {
 	p[node] = position
 }