Creates persistent notification which shows battery level

[wmaciel]

I apologize for taking so long to get to this.

This change is super simple and I think quite a bit of further work could go into this.

As it stands now a notification pops up when the app opens and every time the battery indicator in the app updates, the notification is updated with the current charge of the battery.

I've been reading a little bit about notifications and they could do so much more.

Some things that I think could follow this change:

• Make taping the notification open the app again.
• Change the notification icon to a better one.
• Make the notification display more info if the user expands it.

[kwatkins]

Hmm. Good to see someone working on the notifications, I might just remove what I was doing and go with this. Totally agree we can do more, and should, with notifications. Custom ones can be done with 'remoteviews'. And we should consider making it persistent, showing all battery levels...

[kwatkins]

Looks good! Merging.