Extract patchset in Rietveld URLs better

Parse URL in the form of:
https://domain/<number>/#ps<patchset>

Review-Url: https://codereview.chromium.org/2215433004
diff --git a/tests/git_cl_test.py b/tests/git_cl_test.py
index 286290f..a8c4944 100755
--- a/tests/git_cl_test.py
+++ b/tests/git_cl_test.py
@@ -145,6 +145,8 @@
          123, None, 'codereview.chromium.org')
     test('https://codereview.chromium.org/123/whatever',
          123, None, 'codereview.chromium.org')
+    test('https://codereview.chromium.org/123/#ps20001',
+         123, 20001, 'codereview.chromium.org')
     test('http://codereview.chromium.org/download/issue123_4.diff',
          123, 4, 'codereview.chromium.org',
          patch_url='https://codereview.chromium.org/download/issue123_4.diff')