Fix regex in String#blank?
Fix regex in String#blank?

The reason for previous Opal failure is that `[:space:]` doesn't exist in Javascript regex syntax.
bbatsov/volt,sinventor/volt,askl56/volt,bglusman/volt,alexandred/volt,jfahrer/volt,gabrielrios/volt,voltrb/volt,ahnbizcad/volt,Gaelan/volt,Gaelan/volt,voltrb/volt,askl56/volt,ASnow/volt,merongivian/volt,bglusman/volt,CollaboTree/volt,sinventor/volt,bglusman/volt,orbitalimpact/crystal-meth,RickCarlino/volt,ASnow/volt,thyagobr/volt,matthew342/volt,sinventor/volt,orbitalimpact/crystal-meth,mzdunek93/volt,alexandred/volt,merongivian/volt,nightweb/volt,ahnbizcad/volt,ahnbizcad/volt,RickCarlino/volt,thyagobr/volt,nightweb/volt,askl56/volt,gabrielrios/volt,nightweb/volt,orbitalimpact/crystal-meth,CollaboTree/volt,dummey/volt,matthew342/volt,merongivian/volt,ASnow/volt,Gaelan/volt,dummey/volt,bbatsov/volt,mzdunek93/volt,thyagobr/volt,gabrielrios/volt,jfahrer/volt,bbatsov/volt,jfahrer/volt,matthew342/volt,voltrb/volt,dennym/volt,dummey/volt,RickCarlino/volt,CollaboTree/volt,dennym/volt,alexandred/volt,mzdunek93/volt