Fix missing incrementation in sider.list.List.__iter__()

This function have fetched a few items of the list that is too long
to be fetched at once. Furthermore, this code used the trick to calling
`Session.mark_query()` in the loop and prevent to calling it more than once.
But it doesn't need to do because `mark_query()` was called exactly one time
in the all situation. So I fixed it too.
Add more tests
Merge pull request #6 from Kroisse/fix-list

Fix missing incrementation in sider.list.List.__iter__()
Avoid http://bugs.python.org/issue4806
Apply same kind of patch as c80733ddaf4864 on sider.hash.Hash
Workaround to fetch server info in the pipeline

`redis.client.BasePipeline` (and its children) always return itself
except `BasePipeline.execute()` is called. Because `MULTI/EXEC` commands
of Redis does like this. And, `sider.session.Session.client` can be replaced
with pipeline object in the transaction. Therefore, sometimes
`Session.server_version` returns pipeline object rather than a version string.
Apply same kind of patch as c80733ddaf4864 on sider.set.Set
Add more tests for sorted sets
Fix a wrong usage of StrictRedis.zunionstore()
Merge pull request #7 from Kroisse/fix-update

Replace calls with generators as a variadic args, when passing large data into the collection