Fix callback arguments documentation
Fix callback arguments documentation

Link to all the referenced core objects.
Remove obsolete `http.Client`.
Change `http.ClientResponse` to `http.IncomingMessage`.

Fixes #678.
Closes #721.

rbramwell/request,watson/request,request/request,lxe/request,motopia/request,NewGyu/request,rbramwell/request,HAKASHUN/request,IveWong/request,wakermahmud/request,HAKASHUN/request,manishnakar/request,beni55/request,IbpTeam/node-request,djchie/request,xiwc/request,IveWong/request,pho3nixf1re/request,kublaj/request,LoicMahieu/request,Prasanna-sr/request,simov/request,udp/request,NewGyu/request,calibr/request,Codelegant92/request,faradayio/request,jzaefferer/request,xtidt/request,kevinburke/request,jsifuentes/request,pho3nixf1re/request,Prasanna-sr/request,h1bomb/request,czardoz/request,zodsoft/request,MofeLee/request,xtidt/request,mvnnn/request,kmulvey/request,blabno/request,ryanwholey/request,sean3z/request,request/request,nishant8BITS/request,lxe/request,jzaefferer/request,LoicMahieu/request,kublaj/request,manishnakar/request,Aloomaio/request,chaoliu/request,ryanwholey/request,longwenjunjie/request,xiwc/request,simov/request,not001praween001/request,motopia/request,linalu1/request,zhouweiming/request,neo-z/request,robu3/request,zodsoft/request,paulomcnally/request,neo-z/request,cvibhagool/request,not001praween001/request,zhouweiming/request,pablobrady/request,chaoliu/request,kevinburke/request,h1bomb/request,cvibhagool/request,lalitkapoor/request,wangchi/request,seegno-forks/request,wakermahmud/request,whembed197923/request,IbpTeam/node-request,sean3z/request,Jonekee/request,kmulvey/request,nishant8BITS/request,wangchi/request,Aloomaio/request,czardoz/request,seegno-forks/request,niklabh/request,calibr/request,lalitkapoor/request,MofeLee/request,linalu1/request,phillipj/request,faradayio/request,mvnnn/request,Jonekee/request,whembed197923/request,blabno/request,watson/request,phillipj/request,djchie/request,udp/request,jsifuentes/request,niklabh/request,beni55/request,robu3/request,paulomcnally/request,pablobrady/request,longwenjunjie/request,Codelegant92/request