fixes issue #773

Removed redundant tests in test_validators.py since there's test_isurl.py
Added allowed_tlds from http://data.iana.org/TLD/tlds-alpha-by-domain.txt
Added script to easily update the official_top_level_domains for the future

scripts/parse_top_level_domains.py

@@ -0,0 +1,41 @@
+#!/bin/env python
+# -*- coding: utf-8 -*-
+"""
+Use to update official_top_level_domains in gluon/validators.py
+"""
+
+import itertools
+import operator
+import urllib2
+
+LIMIT = 70
+PREFIX = '    '
+TLDS_URL = 'http://data.iana.org/TLD/tlds-alpha-by-domain.txt'
+
+resp = urllib2.urlopen(TLDS_URL)
+content = resp.read()
+
+valid_lines = [a.strip().lower() for a in content.split('\n') if a.strip() and a.strip()[0] != '#']
+valid_lines += ['localhost']
+
+print 'Fetched TLDs are %s' % len(valid_lines)
+
+results = [list(g) for k, g in itertools.groupby(sorted(valid_lines), key=operator.itemgetter(0))]
+
+output = []
+line = "'%s', "
+
+for a in results:
+    output.append('%s# %s' % (PREFIX, a[-1][0]))
+    thisline = PREFIX
+    for c in a:
+        newline = thisline + line % c
+        if len(newline) > 70:
+            output.append(thisline[:-1])
+            thisline = PREFIX + line % c
+        else:
+            thisline += line % c
+    if thisline:
+        output.append(thisline[:-1])
+
+print '[\n' + '\n'.join(output)[:-1] + '\n]'