Log Message:
audio/ncspot: update to 0.9.1

Mostly a maintenance release. However, due to the migration to rspotify's new
API in 0.11.x many parts of the codebase had to be adapted.

Maintenance
-Stop player when Spotify worker thread dies (#628)
-Update librespot to 0.3.1 (may reduce CPU usage during playback,
 https://github.com/librespot-org/librespot/releases/tag/v0.3.1)
-Major/breaking update to rspotify 0.11.3 (#640)
-Refactoring and other cleanups

Features
-Show playlist owner name (#652)
-Improve README (logo, TOC, layout, syntax) (#644)