Update flights.py to run with python2 and python3
Update flights.py to run with python2 and python3

urllib2 is depreciated in python3.  
Small edit to detect the calling version and import the relevant module.
jprochazka/adsb-feeder,jprochazka/adsb-feeder,jprochazka/adsb-receiver,jprochazka/adsb-feeder,jprochazka/adsb-receiver,jprochazka/adsb-receiver,jprochazka/adsb-feeder,jprochazka/adsb-receiver,jprochazka/adsb-receiver,jprochazka/adsb-feeder