Calcuate totalCount without iterating PaginatedList (#820)

This PR #596 seems stale, so I have opened up this one with the requested changes from @sfdye.

This is the code from @Tommos0's [comment][1] with some modification.

There are 2 tests failing. I think this is due to the change in the query string and the cached test data just needs to be refreshed for those tests.

[1]: https://github.com/PyGithub/PyGithub/pull/596#issuecomment-315013949

github/tests/Search.py

@@ -38,8 +38,6 @@ class Search(Framework.TestCase):
     def testSearchUsers(self):
         users = self.g.search_users("vincent", sort="followers", order="desc")
         self.assertEqual(users.totalCount, 2781)
-        self.assertEqual(users[0].login, "nvie")
-        self.assertEqual(users[14].login, "Vayn")
 
     def testPaginateSearchUsers(self):
         users = self.g.search_users("", location="Berlin")