Been working on this on and off for a while but it's come far enough along that I want to share it with the community.
https://github.com/brettkolodny/gwt
Currently it only supports HS256, HS384, and HS512 but it's been pracitcal enough for me to use it in my work project.
Some of the code is a bit messy but I would love to get some community feedback about the API before I release v1.0!