I love projects like this! Do one thing and do it well. rsvp.js is “A lightweight library that provides tools for organizing asynchronous code. Specifically, it is a tiny implementation of Promises/A and a mixin for turning objects into event targets.” And it looks to do that really well.
These libraries are fantastic study materials for me. With a single goal in mind, you can really get some insight into the style of the developer behind it, and that often shows you how to think about things differently, or at least has you wonder “how the heck is that working?” which in turn most often takes you down a true rabbit hole of education. It’s awesome.