Artist and Track Information Sometimes Missing on Spotify Opening

[corigne]

Spotify takes an agonizingly long time to register the artist and track information with the Mpris player interface in DBus at launch. Depending on how fast your machine spins up the spotify client, it could take upward of a full second for DBus to have all poll-able information about the current track.

I've added a 1.25 seconds sleep between name owner change detection and polling for the track/artist information which appears to give spotify enough time, at least on my devices.

This may not be acceptable for slower devices, though, so I will look into something a little more robust that polls dbus until the artist and track name are not empty strings before updating the module.

See commit d38b192 and 61ee538 for action on this so far.