fix(package): update cross-env to version 5.1.6

Closes #16

Author: greenkeeper[bot]

package.json

@@ -18,7 +18,7 @@
     "babel-preset-es2015": "^6.5.0",
     "babel-preset-react": "^6.5.0",
     "babel-register": "^6.5.2",
-    "cross-env": "^3.1.4",
+    "cross-env": "^5.1.6",
     "dot": "^1.0.3",
     "dustjs-helpers": "^1.7.2",
     "dustjs-linkedin": "^2.7.2",