chore: Don't use the deprecated Buffer constructor

[realityking]

🚀 Why this change?

The Buffer constructor is deprecated (it will likely start throwing warnings in Node.js 10), instead Buffer.{from|alloc|allocUnsafe} should be used.

Discussion of the API change: https://medium.com/@jasnell/node-js-buffer-api-changes-3c21f1048f97
Runtime deprecation planning: nodejs/node#19079

📝 Related issues and Pull Requests

This is also preparation for #975.

✅ What didn't I forget?

• To write docs
• To write tests
• To put Conventional Changelog prefixes in front of all my commits and run npm run lint

[ChALkeR]

Uh-oh. Without this patch, dredd apparently sends a chunk of uninitialized memory as auth headers when configuration.options.user is a number (it's read from a yml config and is typed afaik). Doesn't seem to be serious due to use-cases, but still not a nice thing.

[realityking]

@ChALkeR Only if configuration.options.user is a number. I assume it's a string so it'll be this behaviour: https://nodejs.org/api/buffer.html#buffer_new_buffer_string_encoding

[realityking]

@honzajavorek The tests on Node 8 failed. Could you restart that job?

[honzajavorek]

@realityking Just did :)

[honzajavorek]

if configuration.options.user is a number

Can we just always coerce it to a string in the configuration?

[realityking]

Can we just always coerce it to a string in the configuration?

That'd be possible. Behaviour with the patch as it is would be to throw the error TypeError: "value" argument must not be a number.

[honzajavorek]

LGTM. Thank you! ✨