chore(package): update fetch-mock to version 6.1.0-beta.2

Closes #29

Author: greenkeeper[bot]

package.json

@@ -69,7 +69,7 @@
     "eslint": "^3.14.0",
     "eslint-plugin-ava": "^4.0.1",
     "fake-indexeddb": "^1.0.8",
-    "fetch-mock": "^5.5.0",
+    "fetch-mock": "^6.1.0-beta.2",
     "husky": "^0.12.0",
     "nyc": "^10.0.0",
     "rimraf": "^2.5.4",