Changing filter flow, adding sound support
I added sound support as provided in a PR for terminal-notifier,
compiling it is a paint, but I don't always see just the visual alert on
my monitor setup.
Also fixing (?) the filter flow to how I think it should work to do:
  - Don't alert when I'm talking, I know I'm talking about things in my
    filter
  - Check the channel filter first and toss things if we're not in a
    channel that's appropriate
  - Then check notify_on_nick and alert if someone is talking to us
    (either my_nick or my_nick: plus a space)
  - Finally check and see if the message matches something in our filter
    and alert if it does
This flow works for me, not sure about everyone else