Fail for unsupported OS
Merge pull request #6 from bkkrw/master

Fail for unsupported OS
Security measures + default ntp servers if ntp_servers is undef
Merge pull request #7 from fdammeke/master

Security measures + default ntp servers if ntp_servers is undef
Convert module structure to fixture based setup
Merge pull request #8 from bkkrw/master

Convert module structure to fixture based setup