Downgrade mocha (temp solution to pass tests)

See https://github.com/mochajs/mocha/releases/tag/v5.0.2

Author: gkubisa

package.json

@@ -14,7 +14,7 @@
     "coveralls": "^3.0.1",
     "expect.js": "^0.3.1",
     "istanbul": "^0.4.5",
-    "mocha": "^5.2.0",
+    "mocha": "5.0.1",
     "mongodb": "^3.1.0",
     "sharedb": "^1.0.0-beta",
     "sharedb-mingo-memory": "^1.0.1"