chore(package): update assume to version 2.2.0

Author: greenkeeper[bot]

package.json

@@ -31,7 +31,7 @@
   },
   "homepage": "https://github.com/unshiftio/xhr-response",
   "devDependencies": {
-    "assume": "~2.0.0",
+    "assume": "~2.2.0",
     "istanbul": "~0.4.5",
     "mocha": "~3.5.0",
     "pre-commit": "~1.2.0"