remove hardcoded python3 path in scrapeScenes.py

[ddissett]

the command interpreter set in line 1 of scrapeScenes.py is:

#!/usr/bin/python3

but Python 3 might be installed elsewhere (i.e. /opt/local/bin if using MacPorts). I suggest using this instead:

#!/usr/bin/env python3

so it picks up python3 form your $PATH.