build(deps-dev): bump tslint from 5.12.1 to 5.15.0

Bumps [tslint](https://github.com/palantir/tslint) from 5.12.1 to 5.15.0.
- [Release notes](https://github.com/palantir/tslint/releases)
- [Changelog](https://github.com/palantir/tslint/blob/master/CHANGELOG.md)
- [Commits](palantir/tslint@5.12.1...5.15.0)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Author: dependabot-support

package-lock.json

@@ -51,7 +51,7 @@
     "ts-node": "^8.0.3",
     "tsickle": "^0.34.2",
     "tslib": "^1.9.3",
-    "tslint": "~5.12.1",
+    "tslint": "~5.15.0",
     "typescript": "^3.1.6"
   }
 }