Add missing dep

Author: mjackson

package.json

@@ -29,6 +29,7 @@
     "babel-core": "^6.17.0",
     "babel-eslint": "^7.0.0",
     "babel-loader": "^6.2.4",
+    "babel-plugin-dev-expression": "^0.2.1",
     "babel-preset-es2015": "^6.9.0",
     "babel-preset-es2015-loose": "^8.0.0",
     "babel-preset-react": "^6.5.0",