Merge pull request #10 from unshiftio/greenkeeper/assume-2.0.0

Update assume to the latest version 🚀

Author: 3rd-Eden

package.json

@@ -32,7 +32,7 @@
     "url": "https://github.com/unshiftio/prefixes/issues"
   },
   "devDependencies": {
-    "assume": "~1.5.0",
+    "assume": "~2.0.0",
     "istanbul": "~0.4.5",
     "mocha": "~3.5.0",
     "pre-commit": "~1.2.0"