See issue 57 for discussion and planned improvements.
Updated missing url https://raw.github.com/stamen/modestmaps-js/v0.18.4/modestmaps.min.js to https://cdn.jsdelivr.net/gh/stamen/modestmaps-js/v0.18.4/modestmaps.min.js
https://raw.github.com/stamen/modestmaps-js/v0.18.4/modestmaps.min.js