Algoriddim’s popular DJ app djay 2 ($5) has added more than 20 million new songs in version 2.5 as the developer has partnered with Spotify, giving users a nearly endless amount of songs to mix. That would be enough to qualify for a major update, but the app also adds matching programs, which finds similar songs on Spotify. An all new Audio FX section has been added to the app as well, offering more than 30 new audio effects. New samples and…