Remove malicious dependency

The flatmap-stream package contains malicious code. See [1] for details.

[1] https://www.npmjs.com/advisories/737

Author: migerh

package-lock.json

@@ -51,7 +51,7 @@
     "less": "^3.8.1",
     "less-loader": "^4.1.0",
     "mkdirp": "^0.5.1",
-    "nodemon": "^1.17.5",
+    "nodemon": "^1.18.6",
     "object-assign": "4.1.1",
     "postcss-flexbugs-fixes": "3.2.0",
     "postcss-loader": "2.0.8",