Fix prm being broken on ruby <= 1.9.2.

require_relative is not available prior to this.
Remove unused variables in lib/prm/repo.rb
Bump patch version to 0.2.2
Reintroduce the date variable.

I didn't realise this was being used in a template.
Merge pull request #27 from mfoo/fix-pre-ruby-1.9.2

Fix pre ruby 1.9.2