Added check_redis_version. Fixes #3449

Checking the redis version will warn users that
are using an old version to update. Included
reference to the troubleshooting guide.
Added new output information, fixed typo
Fixed redis-cli check function
Fixed identation...
Added check_redis_version. Fixes #3449

Checking the redis version will warn users that
are using an old version to update. Included
reference to the troubleshooting guide.
Merge branch 'check-redis' of github.com:axilleas/gitlabhq into check-redis
Merge pull request #3602 from axilleas/check-redis

Added check_redis_version to check.rake