rename Walker to Walkable interface

walker/walker.go

@@ -1,13 +1,13 @@
 package walker
 
-// Walker interface
-type Walker interface {
+// Walkable interface
+type Walkable interface {
 	Walk(v Visitor)
 }
 
 // Visitor interface
 type Visitor interface {
-	EnterNode(w Walker) bool               // EnterNode invoked for each node encountered by Walk.
+	EnterNode(w Walkable) bool             // EnterNode invoked for each node encountered by Walk.
 	GetChildrenVisitor(Key string) Visitor // GetChildrenVisitor returns visitor for children nodes
-	LeaveNode(w Walker)                    // LeaveNode invoked after process node
+	LeaveNode(w Walkable)                  // LeaveNode invoked after process node
 }