Update dependency tslint to v5.15.0

Author: renovate-bot

package-lock.json

@@ -50,7 +50,7 @@
     "react": "16.8.6",
     "react-dom": "16.8.6",
     "ts-jest": "23.10.5",
-    "tslint": "5.14.0",
+    "tslint": "5.15.0",
     "tslint-config-prettier": "1.18.0",
     "tslint-eslint-rules": "5.4.0",
     "tslint-plugin-prettier": "2.0.1",