Upgraded to [email protected] to fix GitHub vulnerability warning

Author: twolfson

package.json

@@ -32,7 +32,7 @@
     "spritesheet-templates": "^10.3.0",
     "spritesmith": "^3.4.0",
     "through2": "~2.0.3",
-    "underscore": "~1.8.3",
+    "underscore": "~1.13.1",
     "url2": "~1.0.4",
     "vinyl": "~2.1.0"
   },