fix static VERSION property

src/wechaty.spec.ts

@@ -62,6 +62,10 @@ test('Export of the Framework', async t => {
   t.ok(log,         'should export log')
 })
 
+test('static VERSION', async t => {
+  t.true('VERSION' in Wechaty, 'Wechaty should has a static VERSION property')
+})
+
 test('Config setting', async t => {
   t.ok(config, 'should export Config')
   // t.ok(config.default.DEFAULT_PUPPET  , 'should has DEFAULT_PUPPET')

src/wechaty.ts

@@ -136,7 +136,7 @@ const PUPPET_MEMORY_NAME = 'puppet'
  */
 export class Wechaty extends Accessory implements Sayable {
 
-  public readonly VERSION = VERSION
+  public static readonly VERSION = VERSION
 
   public  readonly state      : StateSwitch
   private readonly readyState : StateSwitch