Upgrade node sass

package.json

@@ -59,7 +59,7 @@
     "karma-coverage-istanbul-reporter": "^2.0.4",
     "karma-jasmine": "~1.1.2",
     "karma-jasmine-html-reporter": "^1.4.0",
-    "node-sass": "^4.14.1",
+    "node-sass": "^6.0.1",
     "protractor": "^5.4.1",
     "ts-node": "~7.0.1",
     "tslint": "~5.11.0",