Add a few more serde integration tests
Add a few more serde integration tests

- A string (will vary on Python version)
- Another unicode string
- A list (pickled)
- A defaultdict (pickled)

ewdurbin/pymemcache,sontek/pymemcache,pinterest/pymemcache,bwalks/pymemcache,sontek/pymemcache,pinterest/pymemcache