Implemented block instruction parsing

src/build/token/Token.go

@@ -11,8 +11,8 @@ type Token struct {
 	Bytes    []byte
 }
 
-// After returns the position after the token.
-func (t *Token) After() int {
+// End returns the position after the token.
+func (t *Token) End() int {
 	return t.Position + len(t.Bytes)
 }