chore(package): update json-server to version 0.15.0

Closes #26

Author: greenkeeper[bot]

package.json

@@ -47,7 +47,7 @@
     "html-webpack-plugin": "^2.28.0",
     "jsdom": "^10.0.0",
     "json-schema-faker": "^0.4.1",
-    "json-server": "^0.10.0",
+    "json-server": "^0.15.0",
     "localtunnel": "^1.8.2",
     "mocha": "^3.2.0",
     "nock": "9.0.13",