Merge pull request #62 from WordPress/update/underscore

chore: update underscore to version `1.9.0`

Author: ntwb

package.json

@@ -38,7 +38,7 @@
     "grunt": "^1.0.2",
     "inquirer": "^5.1.0",
     "request": "^2.83.0",
-    "underscore": "~1.8.3",
+    "underscore": "~1.9.0",
     "underscore.string": "~3.3.4",
     "xmlrpc": "^1.3.1"
   },