Consider removing Buffer from node code, replace with native array type

[ericblade]

More info: https://sindresorhus.com/blog/goodbye-nodejs-buffer

Also would provide a better fix for: #509

The current fix is just to install the type, because it doesn't matter... but it could matter in user code.

[yogeshgadge]

added PR #539

[yogeshgadge]

side observations: root tsconfig.json has types ["mocha", "node"]
probably consider tsconfig.test.json for the mocha tests inside src/

[ericblade]

good idea. there's been some recent upgrades to typescript's handling of nested tsconfig files, too, an update to current ts is probably a good idea too