add Python 3 compatibility

gradint-build/Makefile

gradint-build/samples/utils/README.txt

gradint-build/server/cantonese.py

gradint-build/server/email-lesson.sh

gradint-build/server/espeak.cgi

gradint-build/server/gradint.cgi

gradint-build/server/lesson-table.py

gradint-build/server/safety-check-progressfile.py

gradint-build/server/vocab2html.py

gradint-build/src/booktime.py

gradint-build/src/filescan.py

gradint-build/src/frontend.py

gradint-build/src/lessonplan.py

gradint-build/src/loop.py

gradint-build/src/makeevent.py

gradint-build/src/play.py

gradint-build/src/recording.py

gradint-build/src/sequence.py

gradint-build/src/synth.py

gradint-build/src/system.py