Node 12 support

[CantGetRight82]

There seems to be an issue when used with nodejs 12.4

Just the mention of 'Buffer' inside a plugin, triggers a 'ReferenceError: Buffer is not defined'.
When switching back to nodejs 10 the problem goes away.

[justinmk]

cannot reproduce with the steps given.

[kalekseev]

@justinmk I created a new issue with the same problem but with steps to reproduce #141