Add a deprecation warning when calling Omnibus.root
Add a deprecation warning when calling Omnibus.root

There was already a comment suggesting we do this, so why not do it? :)

Altiscale/omnibus,chef/omnibus,Scalr/omnibus,adamleff/omnibus,intfrr/omnibus,pskrz/omnibus,3ofcoins/chef-omnibus,DataDog/omnibus-ruby,pskrz/omnibus,chef/omnibus,servebox/omnibus,lvfeng1130/omnibus,DataDog/omnibus-ruby,3ofcoins/chef-omnibus,ashhher3/omnibus,mattray/omnibus,mattray/omnibus,rhass/omnibus,servebox/omnibus,higanworks/omnibus,Altiscale/omnibus,rhass/omnibus,strangelittlemonkey/omnibus,lvfeng1130/omnibus,hugosato/omnibus,sh9189/omnibus,hugosato/omnibus,servebox/omnibus,hugosato/omnibus,strangelittlemonkey/omnibus,chef/omnibus,rapid7/omnibus,jamesn/omnibus,mattray/omnibus,lvfeng1130/omnibus,DataDog/omnibus-ruby,szechyjs/omnibus,strangelittlemonkey/omnibus,sh9189/omnibus,Scalr/omnibus,ashhher3/omnibus,jamesn/omnibus,adamleff/omnibus,higanworks/omnibus,sh9189/omnibus,rhass/omnibus,szechyjs/omnibus,ashhher3/omnibus,Scalr/omnibus,higanworks/omnibus,adamleff/omnibus,rapid7/omnibus,szechyjs/omnibus,Altiscale/omnibus,pskrz/omnibus,3ofcoins/chef-omnibus,rapid7/omnibus,jamesn/omnibus,intfrr/omnibus,intfrr/omnibus