[Security] Bump lodash from 4.17.15 to 4.17.21

Bumps [lodash](https://github.com/lodash/lodash) from 4.17.15 to 4.17.21. **This update includes security fixes.**
- [Release notes](https://github.com/lodash/lodash/releases)
- [Commits](lodash/lodash@4.17.15...4.17.21)

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

package.json

@@ -118,7 +118,7 @@
     "graphql": "^0.13.2",
     "graphql-tag": "^2.9.2",
     "isomorphic-fetch": "^2.2.1",
-    "lodash": "^4.17.15",
+    "lodash": "^4.17.21",
     "react": "^16.2.0",
     "react-apollo": "^2.1.9",
     "react-dom": "^16.4.2",