chore(package): update when to version 3.7.8

https://greenkeeper.io/

Author: greenkeeper[bot]

package.json

@@ -29,7 +29,7 @@
     "spike-util": "^0.4.0",
     "sprout": "^1.2.0",
     "webpack": "^1.13.3",
-    "when": "^3.7.7"
+    "when": "^3.7.8"
   },
   "devDependencies": {
     "ava": "^0.18.0",