Added support for env vars in Caddyfile
Added support for env vars in Caddyfile

This is work in progress for #304

cez81/caddy,ollie314/caddy,Karthic-Hackintosh/caddy,yukimochi/caddy,pedronasser/caddy,pyed/caddy,DenBeke/caddy,tw4452852/caddy,eiszfuchs/caddy,devangels/caddy,elcore/caddy,tobya/caddy,DenBeke/caddy,tgulacsi/caddy,dusty/caddy,elcore/caddy,elcore/caddy,hackintoshrao/caddy,devangels/caddy,ollie314/caddy,evermax/caddy,tobya/caddy,cez81/caddy,joshix/caddy,pedronasser/caddy,dusty/caddy,DenBeke/caddy,mem/caddy,pedronasser/caddy,mem/caddy,captncraig/caddy,Karthic-Hackintosh/caddy,joshix/caddy,pyed/caddy,evermax/caddy,tw4452852/caddy,tpng/caddy,mem/caddy,buddhamagnet/caddy,cez81/caddy,joshix/caddy,buddhamagnet/caddy,pyed/caddy,Karthic-Hackintosh/caddy,yukimochi/caddy,tobya/caddy,tobya/caddy,eiszfuchs/caddy,evermax/caddy,hackintoshrao/caddy,ollie314/caddy,tpng/caddy,tw4452852/caddy,tpng/caddy,eiszfuchs/caddy,tw4452852/caddy,dusty/caddy,tgulacsi/caddy,mem/caddy,tpng/caddy,tgulacsi/caddy,Karthic-Hackintosh/caddy,tgulacsi/caddy,captncraig/caddy,pyed/caddy,yukimochi/caddy,captncraig/caddy,dusty/caddy,buddhamagnet/caddy,devangels/caddy,hackintoshrao/caddy,ollie314/caddy,eiszfuchs/caddy,evermax/caddy,DenBeke/caddy,pedronasser/caddy,buddhamagnet/caddy,hackintoshrao/caddy