Update to Redis coobkook

Hello,
   Please consider these updates to the Redis cookbook.  We are using the Redis cookbook with these changes today, and including it with wrapper cookbooks where we need to set attributes differently than the defaults.

- Updated redis.conf.erb from Redis 2.x config
- Added a number of options configurable via attributes, with defaults based on fresh install.
- Added option to specify a package version for installing Redis.  Installs latest if not provided.
- Create db path directory specifically.

Thanks!
Michael Bradshaw
mbradshaw@whitepages.com