Create extended Joi from a new instance of Any (#934)

Fix missing top-level methods

Author: joebalancio

lib/index.js

@@ -186,7 +186,7 @@ internals.root = function () {
 
         this.assert(extensions, root.extensionsSchema);
 
-        const joi = Object.assign({}, this);
+        const joi = Object.create(this);
 
         for (let i = 0; i < extensions.length; ++i) {
             const extension = extensions[i];

test/index.js

@@ -2646,5 +2646,17 @@ describe('Joi', () => {
                 done();
             });
         });
+
+        it('should return a custom Joi as an instance of Any', (done) => {
+
+            const customJoi = Joi.extend({
+                name: 'myType'
+            });
+
+            const Any = require('../lib/any');
+            expect(customJoi).to.be.an.instanceof(Any);
+            done();
+        });
+
     });
 });