Spotify just announced integration with popular DJ software platforms like rekordbox, Serato and djay. This will make it much easier to build out sets from playlists and to do cool stuff like blend tracks.The company says that users "will be able to access their entire library and playlists directly within desktop DJ software," with just one caveat. This is only for Premium subscribers. The integration is available in 51 global markets.It looks pretty easy to get started. Just log into a Premium...