Add error dialogs if requests fail

[ethanmay]

Great idea for an app! Was trying to use this at work and the firewall got in the way of the request to Spotify. Would be nice if there was an error dialog to inform the user that the connection failed!

[joshwcomeau]

oh no! Damn firewalls.

Yeah error-handling in general is sorely lacking from this app. The problem with side projects is your time is limited, so covering edge-cases doesn't often make it in.

Thanks for the heads-up though :)