bump to rg 1.8.15
bump to rg 1.8.15

square/rubygems.org,1337807/rubygems.org,square/rubygems.org,1337807/rubygems.org,square/rubygems.org,1337807/rubygems.org,rubygems/rubygems.org-backup,rubygems/rubygems.org-backup,rubygems/rubygems.org-backup