chore(package): update assume to version 2.2.0

Closes #8

Author: greenkeeper[bot]

package.json

@@ -40,7 +40,7 @@
     "millisecond": "~0.1.2"
   },
   "devDependencies": {
-    "assume": "~1.5.0",
+    "assume": "~2.2.0",
     "istanbul": "~0.4.5",
     "mocha": "~3.1.2",
     "pre-commit": "~1.2.0",