fix(package): update mongodb-runner to version 4.2.1

Closes #80

Author: greenkeeper[bot]

package.json

@@ -59,7 +59,7 @@
     "is-mongodb-running": "0.0.1",
     "lodash": "4.17.3",
     "mocha-lcov-reporter": "1.2.0",
-    "mongodb-runner": "3.4.0",
+    "mongodb-runner": "4.2.1",
     "mongoose": "^4.7.1",
     "passport": "0.3.2",
     "passport-github": "1.1.0",