Bump underscore from 1.9.1 to 1.12.1

Bumps [underscore](https://github.com/jashkenas/underscore) from 1.9.1 to 1.12.1.
- [Release notes](https://github.com/jashkenas/underscore/releases)
- [Commits](jashkenas/underscore@1.9.1...1.12.1)

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

Author: dependabot[bot]

package-lock.json

@@ -11,7 +11,7 @@
     "react": "^15.1.0",
     "react-datepicker": "^0.29.0",
     "react-dom": "^15.1.0",
-    "underscore": "^1.8.3",
+    "underscore": "^1.12.1",
     "whatwg-fetch": "^1.0.0"
   },
   "license": "MIT",