Add unmodified /etc/default/redis-server file
Add redis ulimit attribute to default/redis-server template
Add default/redis-server template to server recipe
Set ulimit attribute default to empty

This will result in ulimit not being set in the redis configuration.
Add ulimit to attribute list in REAMDE.md
Add note regarding the ulimit attribute to README.md
Merge pull request #4 from svend/t_ulimit

Add redis attribute to set ulimit