Changed URL validation to use urlparse instead of regex for spliting the URL

Enabled test_is_url in Python 3 since it is now passing
This might be one of the last fixes to #1353
Fixes #1598

gluon/tests/__init__.py

@@ -24,7 +24,7 @@ from .test_web import *
 from .test_sqlhtml import *
 from .test_scheduler import *
 from .test_cron import *
+from .test_is_url import *
 
 if sys.version[:3] == '2.7':
-    from .test_is_url import *
     from .test_old_doctests import *