Modernize codebase

[jimmywarting]

Summary:

• Updated all dep
• Switched to const, let, class + extend
• removed inherits and writable-stream
• depends on builtin stream + buffer instead of polyfill (to always get newest version and fewer dependency installs)
• tested using standard --fix index.js && npx node@10 index.js && npm run test
• The hole test file remains the same to prove that everything works as before (only change was to use node:stream instead)
• know you use standard.js in some projects so i applied it using latest (16) version
• it no longer use new Buffer() constructor
• update code examples in readme

closes #35
closes #10