Add cucumber:mongo script

Following @appinteractive's suggestions

`|| sleep infinity` here will make sure the command for starting mongo
won't terminate the parallel execution of `concurrently`. That would be
the case if your mongo is already running, e.g. because of a system-wide
mongodb daemon. But we don't want to terminate the commmand because that
would in turn terminate `concurrently`. Instead we want the last command
`cucumber-js` to exit first.

Author: roschaefer

package.json

@@ -46,7 +46,8 @@
     "dev:win": "npm run clear && concurrently \"mongod --dbpath /data/db\" \"wait-on tcp:27017&&cross-env NODE_ENV=development&&cross-env DEBUG=feathers&& nodemon --inspect server/\"",
     "mocha": "npm run clear && $npm_package_config_mocha",
     "mocha:mongo": "$npm_package_config_concurrently '$npm_package_config_mongoDev &>/dev/null' 'wait-on tcp:27017 && npm run mocha'",
-    "cucumber": "npm run clear && concurrently --kill-others --success first 'cross-env NODE_ENV=test node server/' 'wait-on tcp:3030 && cross-env NODE_ENV=test cucumber-js'"
+    "cucumber": "npm run clear && concurrently --kill-others --success first 'cross-env NODE_ENV=test node server/' 'wait-on tcp:3030 && cross-env NODE_ENV=test cucumber-js'",
+    "cucumber:mongo": "npm run clear && concurrently --kill-others --success first '$npm_package_config_mongoDev &>/dev/null || sleep infinity' 'wait-on tcp:27017 && cross-env NODE_ENV=test node server/' 'wait-on tcp:3030 && cross-env NODE_ENV=test cucumber-js'"
   },
   "config": {
     "mongoDev": "mongod --dbpath data --quiet",