NotifySend support for app name

[gabrielfern]

Hello, notify-send has an option to set the app name, but I couldn't be able to pass that option through node-notifier, so I made the additions that enables people to use that option if they want to, using node-notifier.
Although it seems notify-send man page doesn't say anything about this option, it's definitively there, I tested the option under some Ubuntu based systems and notify-send recognizes the option, also you can find information about the option from other sources like this one notify-send options.
One thing this option does is let you change the "notify-send" default app name, that shows in the notification no matter what in some notifications system.
For example, executing notifier.notify({title: 'Hello Message', message: 'This is a node-notifier message'}) and we get:

But after these changes, you can do notifier.notify({title: 'Hello Message', message: 'This is a node-notifier message', 'app-name': 'node-notifier'}) to get:

screenshots taken from KDE plasma, and ubuntu based system

[mikaelbr]

Thanks! Took long to merge this, but looks good to me.