refactor(server): make with_listener a free function
refactor(server): make with_listener a free function

Allow a Server to operate without requiring the entire Server struct
to move into the with_listener function (instead only the handler
function needs to move). This, allows other members to not move, or
move separately, which will be needed for the next commit.  See #471

tempbottle/hyper,tshepang/hyper,markuskobler/hyper,bheesham/hyper,Keats/hyper,reem/hyper,Twey/hyper,fengsp/hyper,tshepang/hyper,fuchsnj/hyper,golddranks/hyper,Twey/hyper,nstoddard/hyper,lame-nickname/hyper,hannobraun/hyper,giftcards/hyper,mitsuhiko/hyper,tshepang/hyper,yangxingpping/hyper,TimNN/hyper,pyfisch/hyper,hyperium/hyper,ianks/hyper,golddranks/hyper,yazaddaruvala/hyper,golddranks/hyper,Twey/hyper,achanda/hyper,jmmaranan/hyper,youprofit/hyper,manuel-woelker/hyper,nstoddard/hyper,erickt/hyper,nickgonzales/hyper,Keats/hyper,hannobraun/hyper,hannobraun/hyper,bonifaido/hyper,markuskobler/hyper,mneumann/hyper,yazaddaruvala/hyper,nickgonzales/hyper,peterhj/hyper,softprops/hyper,mre/hyper,mlalic/hyper,mlalic/hyper,hyperium/hyper,hyperium/hyper,rschulman/hyper,mfeckie/hyper,fhahn/hyper,markuskobler/hyper,clatour/hyper,nickgonzales/hyper,Keats/hyper,sfackler/hyper,steveklabnik/hyper