require rubygems in the Rakefile for testing

...as both experience and
https://github.com/puppetlabs/puppetlabs_spec_helper#usage say we should :)
mark perlbrew user/group as system; allow system to assign ids

On many systems we will want to allow the system to choose a numeric
user/group id for us, so as to avoid any conflicts.  And I suspect we always
want to mark this account as a system account, as that has special
implications.
update tests for new user/group options
Merge pull request #14 from perl-puppet/topic/rakefile-updates-for-testing

require rubygems in the Rakefile for testing
Merge pull request #15 from perl-puppet/topic/allow-system-ids

mark perlbrew user/group as system; allow system to assign ids