Include Specinfra::Helper::Set explicitly
Include Specinfra::Helper::Set explicitly

Ref serverspec/specinfra#249

serverspec/serverspec,ihassin/serverspec,ShawInnes/serverspec,tacahilo/serverspec,mekf/serverspec,higanworks/serverspec,uroesch/serverspec,inokappa/serverspec,RoboticCheese/serverspec,minimum2scp/serverspec,aschmidt75/serverspec,elibus/serverspec,mizzy/serverspec,DarrellMozingo/serverspec,pfaffle/serverspec,supertylerc/serverspec,sergueik/serverspec,Plus81/serverspec