Update terminal-notifier to alerter

[foxt]

Terminal-notifier has been updated to remove most of its features with interaction.

https://github.com/vjeantet/alerter should be used instead as it has the features of terminal-notifier plus better interaction.

[mikaelbr]

I looked into alerter earlier, but to me it looks like the terminal notifier version node-notifier uses is "newer" than the alterter bundle? And does alerter still have the memory leak from earlier terminal-notifier?