Revert "removed ruby 1.8.6 from CI due to Rack 1.2.2 not being compatible"
Revert "removed ruby 1.8.6 from CI due to Rack 1.2.2 not being compatible"

This reverts commit 1f0537f7d6526a03778c25272d6d508428a891ee.

ekampp/faraday,luvtechno/faraday,prcongithub/faraday,grosser/faraday,O-I/faraday,mehulkar/faraday,ru-faraon/Faraday-is-an-HTTP-client,prcongithub/faraday,pvdb/faraday,jhass/faraday,davidcornu/faraday,nevans/faraday,coinbase/faraday,AvaelKross/faraday,stayhero/faraday,zhaoxl/faraday,customink/faraday,jrafanie/faraday,santiagodoldan/faraday,daviswahl/faraday,zanker/faraday,mehulkar/faraday,apepper/faraday,ngpestelos/faraday,iamjarvo/faraday,travis-repos/faraday,hstrowd/faraday,apepper/faraday,engineyard/faraday,flower-pot/faraday,davoclavo/faraday,pvdb/faraday,ru-faraon/Faraday-is-an-HTTP-client,ngpestelos/faraday,flower-pot/faraday,zhaoxl/faraday,mauricionr/faraday,petems/faraday,santiagodoldan/faraday,zanker/faraday,davoclavo/faraday,engineyard/faraday,lgierth/faraday,stayhero/faraday,hstrowd/faraday,hrysd/faraday,spyofchina/faraday,AvaelKross/faraday,jhass/faraday,daviswahl/faraday,coinbase/faraday,petems/faraday,whomwah/faraday,O-I/faraday,luvtechno/faraday,lostisland/faraday,davidcornu/faraday,ekampp/faraday,grosser/faraday,hrysd/faraday,nevans/faraday,pcarrier-packaging/deb-ruby-faraday,customink/faraday,avdi/faraday,pcarrier-packaging/deb-ruby-faraday,jrafanie/faraday,mauricionr/faraday,spyofchina/faraday,iamjarvo/faraday,lostisland/faraday