improve upgrade readme
improve upgrade readme

Geoion/AutobahnPython,bencharb/AutobahnPython,oberstet/autobahn-python,nucular/AutobahnPython,tomwire/AutobahnPython,hzruandd/AutobahnPython,ttimon7/AutobahnPython,dash-dash/AutobahnPython,Jenselme/AutobahnPython,crossbario/autobahn-python,dash-dash/AutobahnPython,tavendo/AutobahnPython,iffy/AutobahnPython,schoonc/AutobahnPython,iffy/AutobahnPython,claws/AutobahnPython,jvdm/AutobahnPython,oberstet/autobahn-python,iffy/AutobahnPython,dash-dash/AutobahnPython,inirudebwoy/AutobahnPython,crossbario/autobahn-python,mcfletch/AutobahnPython,iffy/AutobahnPython,RyanHope/AutobahnPython,meejah/AutobahnPython,luhn/AutobahnPython,markope/AutobahnPython,claws/AutobahnPython,mcfletch/AutobahnPython,dash-dash/AutobahnPython,crossbario/autobahn-python,oberstet/autobahn-python