A few changes to make things work and test with Node 4, 5, 6

.travis.yml

@@ -1,6 +1,8 @@
 language: node_js
 node_js:
-  - "5.11"
+  - "4"
+  - "5"
+  - "6"
 sudo: false
 before_script:
   - make clean

modules/actions/circularize.js

@@ -7,11 +7,10 @@ import {
     polygonArea as d3polygonArea,
     polygonHull as d3polygonHull,
     polygonCentroid as d3polygonCentroid
-} from 'd3-polygon';
+} from 'd3';
 
 
-export function Circularize(wayId
-  , projection, maxAngle) {
+export function Circularize(wayId, projection, maxAngle) {
     maxAngle = (maxAngle || 20) * Math.PI / 180;
 
     var action = function(graph) {

modules/behavior/breathe.js

@@ -1,5 +1,5 @@
 import * as d3 from 'd3';
-import { transition as d3transition } from 'd3-transition';
+import { transition as d3transition } from 'd3';
 import _ from 'lodash';