OpenBSD 5.6 may not have a /etc/sysctl.conf by default, therefore
make sure it exists, by creating it, if it doesn't, before attempting
to set sysctl variables.

move the file resource for sysctl.conf to the sysctl::params class.
Merge pull request #28 from buzzdeee/master

create /etc/sysctl.conf if it doesn't yet exist