Normalizing whitespace
Implementing SCAN, SSCAN, HSCAN, and ZSCAN

- refactoring reply_zset to stay DRY but fit my needs
- adding reply_map for easy handling of compound results
- adding unit tests
Fixing *SCAN tests for python 2.6 and 3.3
Merge pull request #56 from taylorbarstow/master

Implementing SCAN commands