use safe-buffer module to make Buffer.from() available in old versions of Node.js

[Trott]

No description provided.

[Trott]

(Happy to modify it so it only touches the tests if you'd prefer to not add a module to the actual library code, since there's already code in there to avoid Buffer constructor if Buffer.from() exists.)

[ChALkeR]

@Trott I specifically patched this in #17 without extra deps.

A one-liner shouldn't require an extra dependency.
Perhaps move that to dev deps only, if it's required for tests? (And leave index.js as-is).

[Trott]

@ChALkeR Sure, done.

[Trott]

I think since #17 landed, this is obsolete but if I'm mistaken, by all means, re-open.