Pyssdb Versions Save

• Fixes: Some SSDB errors give no reasons
• Fixes: zget return the score, which is an integer

Full list of changes: https://github.com/ifduyue/pyssdb/compare/v0.1.1...v0.1.2

• Fixes #2: close a connection if any error occurs.

• support new commands
• set like commands return 1 other than '1'.
• bugfix: pip install pyssdb README.rst not found.