use ujson when available for WAMP serializer
use ujson when available for WAMP serializer

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