Try updating node version on circle to resolve failure

circle.yml

@@ -6,6 +6,8 @@ machine:
       oraclejdk8
   python:
     version: 2.7.3
+  node:
+    version: 4.4.3
 dependencies:
   override:
     - sudo apt-get purge mongodb-org*

package.json

@@ -6,8 +6,8 @@
   "repository": "https://github.com/metabase/metabase",
   "license": "private",
   "engines": {
-    "node": "4.2.2",
-    "npm": "2.14.7"
+    "node": "4.4.3",
+    "npm": "2.15.1"
   },
   "dependencies": {
     "ace-builds": "^1.2.2",