Feature #79 sudo users

Another go at #79

It introduces a small cookbook "sysadmins" that takes sysadmins from the node json file and creates these on the server.

Please have a look and tell me what you think. If you like, I will add a commit that adds this cookbook to the base role and bump the version.

I could not find any tests in the main repo, but maybe I am looking wrong? Am I supposed to run/add tests? And if so, where?

I'm not sure if I understand your question. The reason I made this `false`, is to make sure that all sudo-users have to provide their password in order to gain sudo-rights. This is the "Default Ubuntu Way". Somehow, the chef-sudo-cookbook changes this and kindof "breaks" the standard Ubuntu way. 

Users can still choose passwordless sudo-usage, if they really don't like the Default Ubuntu Way by changing this setting in the node configuration.