update README to show how to pass options

Author: pradel

packages/accounts-mongo/README.md

@@ -34,7 +34,8 @@ const db = await mongodb.MongoClient.connect(process.env.MONGO_URL);
 const client = await mongodb.MongoClient.connect(process.env.MONGO_URL);
 const db = client.db('my-db-name');
 
-const accountsServer = new AccountsServer({ db: new MongoDBInterface(db) });
+const accountsMongo = new Mongo(db, options);
+const accountsServer = new AccountsServer({ db: accountsMongo });
 ```
 
 The users will be saved under the `users` collection.

packages/accounts-mongo/package.json

@@ -59,7 +59,6 @@
     "coveralls": "3.0.0",
     "husky": "0.14.3",
     "jest": "22.4.2",
-    "jest": "21.2.1",
     "prettier": "1.11.1",
     "pretty-quick": "1.4.1",
     "ts-jest": "22.4.1",