make hash take default settings as well

[seiyria]

currently the generic notify function does not use the global settings, and it probably should.

[jacqueslareau]

I think that a method to use the plain pnotify object is useful. But maybe we could add another method that extends global settings with the provided hash.

[seiyria]

Please do. I often have to use the notify function and I would like my
defaults to hold when I do, since there are a lot of them.

[jacqueslareau]

I added this function here: https://github.com/jacqueslareau/angular-pnotify