Merge pull request #4 from andschwa/ids

Parameterizing first/last valid user/group IDs
Merge pull request #6 from andschwa/ssl-fix

Refactoring SSL setup
added contributors section with first contributor
Parameterizing auth-worker user and group

Using 'dovecot::config::dovecotcfsingle' and selector to more easily
remove these parameters if set to 'undef'.