Update zulip.com/integrations link to point to zulipchat.com.

zulip.com will stop running at some point in the near future, and we
don't want these links to break.

api/integrations/hg/zulip-changegroup.py

@@ -24,7 +24,7 @@
 #
 #
 # This hook is called when changesets are pushed to the master repository (ie
-# `hg push`). See https://zulip.com/integrations for installation instructions.
+# `hg push`). See https://zulipchat.com/integrations for installation instructions.
 from __future__ import absolute_import
 
 import zulip

docs/architecture-overview.md

@@ -167,7 +167,7 @@ Redis is used for a few very short-term data stores, such as in the
 basis of `zerver/lib/rate_limiter.py`, a per-user rate limiting scheme
 [example](http://blog.domaintools.com/2013/04/rate-limiting-with-redis/)),
 and the [email-to-Zulip
-integration](https://zulip.com/integrations/#email).
+integration](https://zulipchat.com/integrations/#email).
 
 Redis is configured in `zulip/puppet/zulip/files/redis` and it's a
 pretty standard configuration except for the last line, which turns off

zerver/tests/test_upload.py

@@ -494,7 +494,7 @@ class UploadTitleTests(TestCase):
         self.assertEqual(url_filename("http://localhost:9991/user_uploads/1/LUeQZUG5jxkagzVzp1Ox_amr/dummy.txt"), "dummy.txt")
         self.assertEqual(url_filename("http://localhost:9991/user_uploads/1/94/SzGYe0RFT-tEcOhQ6n-ZblFZ/zulip.txt"), "zulip.txt")
         self.assertEqual(url_filename("https://zulip.com/user_uploads/4142/LUeQZUG5jxkagzVzp1Ox_amr/pasted_image.png"), "pasted_image.png")
-        self.assertEqual(url_filename("https://zulip.com/integrations"), "https://zulip.com/integrations")
+        self.assertEqual(url_filename("https://zulipchat.com/integrations"), "https://zulipchat.com/integrations")
         self.assertEqual(url_filename("https://example.com"), "https://example.com")
 
 class SanitizeNameTests(TestCase):