use builded lib instead of source in core tests

Author: Kuntsevich Andrei

test/lib/index.test.js

@@ -1,5 +1,5 @@
 var expect = require('chai').expect;
-var validate = require('../../lib');
+var validate = require('../../index.js');
 describe('validate', () => {
   it('should be a function', () => expect(validate).to.be.a('function'));