Add babel-runtime to run tests on node 4.2

Author: dabroek

package.json

@@ -24,6 +24,7 @@
     "babel-plugin-external-helpers": "^6.22.0",
     "babel-plugin-transform-runtime": "^6.23.0",
     "babel-preset-es2015": "^6.24.1",
+    "babel-runtime": "^6.26.0",
     "cache-manager": "^2.4.0",
     "coveralls": "^2.13.1",
     "jest": "^20.0.4",