Bump buffer-writer version (#1764)
Bump buffer-writer version (#1764)

Fixes the deprecation warning for using `new Buffer`.

The change is semver major in buffer-writer since we dropped support for node < 4.x, but otherwise it's a non-breaking change.  Since node-postgres already requires node >= 4.x it's fine.
brianc/node-postgres,brianc/node-postgres