playTrack ({ state, dispatch }, track) {
      const trackData = state.tracks[track]
      if (!trackData) {
        throw new Error('Invalid track specified')
      }

      const plays = Array.from(trackData.keys())
        .map(id => dispatch('playSound', id))

      return Promise.all(plays)
    }
Plays the specified track. Track must be valid. Noop when already playing.

@param track {string} name of track to play
@throws {Error} when invalid track specified
@return Array of IDs of the played sounds