datatype.test: use predefined date

Some databases are storing the value in UTC (not ISO) format,
and truncating the values. Even though this is technically
unavoidable, it does fail strict string equality.

test/datatype.test.js

@@ -55,7 +55,7 @@ describe('datatypes', function() {
     });
 
   it('should keep types when get read data from db', function(done) {
-    var d = new Date, id;
+    var d = new Date('2015-01-01T12:00:00'), id;
 
     Model.create({
       str: 'hello', date: d, num: '3', bool: 1, list: ['test'], arr: [1, 'str'],