added docstrings & authorship information
improved inline commenting/documentation
separated modular notifier code into separate file
basic .gitignore
replace print with sys.stdout.write for outputting terminal bell character, to avoid extraneous newline
docstrings added to notifiers
removed extraneous TODO
removed testing exception from NSBeep
more useful error message for trying Notification Centre on non-compatible machine
changed NC error message for non OS X 10.8+ machines
added error message if an invalid notifier name is used
NotificationCentre added sound/silent option, cleaned slightly