Slack lets coworkers start ringing one another

Companies that use Slack for internal collaboration now have a new way to communicate. The startup began rolling out a voice calling feature on Wednesday that lets people talk to each other one-on-one or in group conference calls.It’s a transition for Slack, which until now has focused mainly on text communication. The company revealed yesterday that allowing people to make calls is a big part of its roadmap for 2016, and this initial beta launch is a first step.Right now, it's available t