8.0.0

What's Changed

• Infer contentType from playQueue items (#457) @maykar
• Lint example scripts (#456) @emontnemery
• Revert "Lint example scripts" (#455) @emontnemery
• Lint example scripts (#452) @emontnemery
• Bump pylint to 2.6.0 (#454) @emontnemery
• Remove unintended 'async' from listener interfaces (#453) @emontnemery
• Update BubbleUPNP example (#451) @emontnemery
• Refactor listeners and controllers as ABCs (#450) @emontnemery
• Add more google devices to consts (#448) @theychx
• Make current_time optional when loading or queing media (#446) @emontnemery