Paiwei fix admin client

- add/fix README.md
- fix clone() method
- add info() method to show host, port, and timeout this admin
- fix seg fault of maxqueue(), workers(), etc. (mostly due to incorrect ref count / parameter passing / eom_mark)
- complete most of the unittests except 'cancel job', 'show jobs', and 'show unique jobs' (unknown commands for older version of gearmand)
- add a server sandbox to testing code
- fix docstrings