Buffered results missing properties for features

[liebrand]

First I found out the hard way that the default version of turf-buffer inside turf is an old one, which is buggy. After locally installing the latest version (1.1.0) of turf-buffer I'm getting much better results. But I spotted a bug around properties.

Line 75 of index.js has:
properties: {}

which should be:
properties: feature.properties