Buffering progress, attribute state change events, and fixes

• Hook up media-buffered attribute to progress background (#185) 52ccddc
• Fix custom element constructor attribute bug (#194) 3cbff95
• fix(user-inactive-autoplay): Make default user-inactive true to handle programmatic play starts + hiding controls. 8e6ca16
• fix(user-inactive-poster): treat slotted poster like slotted media for pointer-events for user-inactive behavior. 95d4126
• fix: use mouseleave instead of mouseout b55da54
• feat(state-change-events): Add example that updates table based on state change events. 1474d45
• feat(state-change-events): Add initial infrastructure to dispatch state change events based on ui attrs + user-inactive. 6b2e422

v0.5.3...v0.5.4