bump grunt-contrib-compress to ~0.13.0

package.json

@@ -37,7 +37,7 @@
     "grunt-autoprefixer": "~2.0.0",
     "grunt-banner": "~0.2.3",
     "grunt-contrib-clean": "~0.6.0",
-    "grunt-contrib-compress": "~0.12.0",
+    "grunt-contrib-compress": "~0.13.0",
     "grunt-contrib-concat": "~0.5.0",
     "grunt-contrib-connect": "~0.9.0",
     "grunt-contrib-copy": "~0.7.0",