global leaks

[tjwebb]

When I have mocha check for global leaks, it reports this:

     Error: global leaks detected: tileliveProtocols, __core-js_shared__

Why does tilelive insert values into the global namespace? This is bad practice, and I've never seen mocha throw this error with any other node module.

[tjwebb]

Right here: https://github.com/mapbox/tilelive/blob/master/lib/tilelive.js#L9