Add optional UPnP auto discovery

[dubocr]

Hi,

I've added UPnP auto discovery feature to your awesome module. This avoid providing static IP adresse which can change over the time. Also add en event emitter to allow dependents modules to track TV availability state.

Best,

[dubocr]

Dear Andrei,

This pull is fully backward compatible with your version and don't need any merge. Is it possible to publish it on npm allowing everybody to use it without publishing my own version on nom that will be confusing for users.

Thank you in advance.