v2.0.0

Added

• Speech notifications.
• Slack notifications.
• Optionally set default notification type(s) through NOTI_DEFAULT env var.
• Multi-notification support.
• Other configuration through environment variables.
• Contributing document.
• Change log.

Changed

• On OS X, the notification sound must now be set in the environment variable,
  NOTI_SOUND.
• On OS X, instead of AppleScript, banner notifications are triggered with
  Object-C, which shows (nicer) Terminal icon.

Removed

• -f flag for OS X. This caused unexpected behavior for people who use iTerm2.
• OS X-specific flags and usage text from Linux and FreeBSD help.