Bump lodash from 4.17.4 to 4.17.21

Bumps [lodash](https://github.com/lodash/lodash) from 4.17.4 to 4.17.21.
- [Release notes](https://github.com/lodash/lodash/releases)
- [Commits](lodash/lodash@4.17.4...4.17.21)

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

Author: dependabot[bot]

package-lock.json

@@ -26,7 +26,7 @@
     "ethereumjs-abi": "^0.6.4",
     "ethereumjs-testrpc": "^6.0.3",
     "ethereumjs-util": "^5.1.2",
-    "lodash": "^4.12.0",
+    "lodash": "^4.17.21",
     "mocha": "^4.0.1",
     "q": "^1.5.1",
     "should": "^8.3.1",