chore(package): update @turf/centroid to version 6.0.0 (#747)

Author: greenkeeper[bot]

package.json

@@ -43,7 +43,7 @@
   },
   "devDependencies": {
     "@mapbox/mapbox-gl-draw-static-mode": "^1.0.1",
-    "@turf/centroid": "^5.0.4",
+    "@turf/centroid": "^6.0.0",
     "babel-core": "^6.9.1",
     "babel-eslint": "^7.1.0",
     "babel-plugin-__coverage__": "^11.0.0",