Update documentation

main.go

-// Example program to demonstrate the generator
+// Example program to demonstrate the modules
 package main
 
 import (

thing.go

 package main
 
+// Thing is a thing
 type Thing struct {
 	Id     int64
 	Name   string `description:"Name of the thing"`

user.go

 package main
 
+// User is a user
 type User struct {
 	Id     int64
 	Name   string   `description:"Name of the user"`