Refresh rather than reauthorize

[pixelchai]

https://github.com/pixelzerg/NightBotNowPlaying/blob/bc30d297b4d3eded2ff4d8f9ec5e4f0fa791cab0/nowplaying.py#L125-L129

[pixelchai]

Low priority because the auth code usually takes a month to expire and it doesn't take too long to re-auth. Let me know if there is any interest in this enhancement, though