Fix plugin spec to run on ruby 1.8+
Fix plugin spec to run on ruby 1.8+

celsworth/roda,janko-m/roda,celsworth/roda,johan--/roda,Freaky/roda,janko-m/roda,johan--/roda,celsworth/roda,mikz/roda,Freaky/roda,jeremyevans/roda,mikz/roda,kematzy/roda,janko-m/roda,johan--/roda,jeremyevans/roda,mikz/roda,kematzy/roda,duykhoa/roda,duykhoa/roda,jeremyevans/roda,duykhoa/roda,Freaky/roda,kematzy/roda