Turfjs/turf-bboxPolygon — pull request #1 by jakeorr (2014-06-13 21:20:23+00:00)
Title: Returning valid geojson polygon by closing the returned shape.

From: http://geojson.org/geojson-spec.html

"For type "Polygon", the "coordinates" member must be an array of LinearRing coordinate arrays."

and

"A LinearRing is closed LineString with 4 or more positions. The first and last positions are equivalent (they represent equivalent points)."