Buffer constructor runtime deprecation - this package emits a warning on Node 10

Hey from Node.js here!, 

Starting on Node 10 this package will emit deprecation warnings.  See [this guide](https://github.com/ChALkeR/safer-buffer/blob/master/Porting-Buffer.md) on what you should do in order to migrate to `Buffer.alloc`/`Buffer.from`. 

See https://github.com/nodejs/node/issues/19079 for discussion around this change and why we can't make `new Buffer` work