Added Kore.com to API Clients list.

We are Kore, new enterprise-oriented messaging solution that offers business professionals and teams security and control—so they can collaborate, communicate and get stuff done like never before. We have used your API to create an integration with Gitlab, starting off with providing alerts for a repository update, and the ability to create an issue, right within the Kore messaging environment. This would provide more stickiness and value to our mutual customers. We launched a month ago and based on our discussion a while back, submitting this merge request.