add gitIgnore config

added config.rb to the GitIgnore to avoid send any private data  by
mistake
added support for Redis metrics

Added the option to select redis or memcache engine from Elasticache
using params.
Improved doc into ElestiCache script

Added the new way to run the script if PullRequest be approved for add support to Redis
Merge pull request #13 from cdgraff/master

Added Redis support to ElastiCache script.  Thanks @cdgraff!