fix(): updated xml2js dependency

Verison of xml2js we were on had a very broad semver range for its
dependency on xmlbuilder, which has had several breaking changes.
Update to narrow that range. Related:
oozcitak/xmlbuilder-js#111.

package.json

@@ -76,7 +76,7 @@
     "unzip2": "0.2.5",
     "vinyl-fs": "1.0.0",
     "winston": "1.1.2",
-    "xml2js": "0.4.4"
+    "xml2js": "0.4.16"
   },
   "devDependencies": {
     "jasmine-node": "1.14.5",