Use lodash 4.17.19.

See https://github.com/commonmark/commonmark-spec-web/security/dependabot/1

Author: jgm

dingus/bower.json

@@ -5,6 +5,6 @@
   "dependencies": {
     "bootstrap": "^3.4.1",
     "jquery": "^3.1.1",
-    "lodash": "^4.17.11"
+    "lodash": "^4.17.19"
   }
 }