tweak godoc

zero/string.go

@@ -1,7 +1,7 @@
 // Package zero provides a convenient way of handling null values.
 // Types in this package consider empty or zero input the same as null input.
 // Types in this package will encode to their zero value, even if null.
-// Use the nuller subpackage if you don't want this.
+// Use the null parent package if you don't want this.
 package zero
 
 import (