Lazily read "hub.host" configuration only when necessary
Lazily read "hub.host" configuration only when necessary

For speed, we want to reduce the number of shelling out to git in a
single invocation of hub, and reading from "hub.host" is unnecessary if
the current hostname matches the default host ("github.com"), which is
the most common case.

AndBicScadMedia/hub,codydaig/hub,whilp/hub,isundaylee/hub,pwaller/hub,sferik/hub,boris-rea/hub,haikyuu/hub,elancom/hub,AndBicScadMedia/hub,jingweno/hub,RichardLitt/hub,sferik/hub,hopil/hub,terry2000/hub,nlutsenko/hub,boris-rea/hub,adjohnson916/hub,nmfzone/hub,tomasv/hub,sbp/hub,dongjoon-hyun/hub,hb9kns/hub,pwaller/hub,ASidlinskiy/hub,nlutsenko/hub,ryo33/hub,cpick/hub,github/hub,naru0504/hub,SanCoder-Q/hub,elancom/hub,pcorpet/hub,aereal/hub,AndBicScadMedia/hub,naru0504/hub,elancom/hub,pankona/hub,hb9kns/hub,ASidlinskiy/hub,rlugojr/hub,tomasv/hub,jingweno/hub,haikyuu/hub,aspiers/hub,jingweno/hub,whilp/hub,RichardLitt/hub,github/hub,cpick/hub,ZenPayroll/hub,dongjoon-hyun/hub,nlutsenko/hub,SanCoder-Q/hub,pwaller/hub,aereal/hub,dev4mobile/hub,aereal/hub,ZenPayroll/hub,Gusto/hub,github/hub,jpkrohling/hub,tomasv/hub,xantage/hub,aspiers/hub,sideci-sample/sideci-sample-hub,sideci-sample/sideci-sample-hub,pcorpet/hub,haikyuu/hub,aspiers/hub,adjohnson916/hub,jpkrohling/hub,sbp/hub,SanCoder-Q/hub,ryo33/hub,terry2000/hub,sbp/hub,xantage/hub,pcorpet/hub,jpkrohling/hub,dongjoon-hyun/hub,RichardLitt/hub,hb9kns/hub,isundaylee/hub,ryo33/hub,hopil/hub,codydaig/hub,rlugojr/hub,Gusto/hub,hopil/hub,pankona/hub,github/hub,rlugojr/hub,isundaylee/hub,naru0504/hub,terry2000/hub,boris-rea/hub,nmfzone/hub,xantage/hub,pankona/hub,whilp/hub,dev4mobile/hub,nmfzone/hub,adjohnson916/hub,dev4mobile/hub,codydaig/hub,ASidlinskiy/hub,cpick/hub