Instagram’s co-founders built a powerful and useful tool for recommending news to readers — but could never quite get it to scale. Yahoo has hundreds of millions of readers — but could use a dose of tech-forward cool to separate it from all the internet’s other news aggregators. And so, the two sides are joining forces: Yahoo is acquiring Artifact, the companies announced on Tuesday.The two sides declined to share the cost of the acquisition, but both made clear Yahoo is acquiring Artifact’s tec...