title: winston-mongodb error after initializing
body: <p>I'm trying to configure a basic winston logger but keep getting the same error.</p>
  
  <p>All I have so far to configure it is this</p>
  
  <pre><code>var winston = require('winston');
  var mongoLog = require('winston-mongodb').MongoDB;
  var appSettings = require('./appSettings');
  
  var logger = new (winston.Logger)();
  logger.add(mongoLog, {
     db: appSettings.database,
     host: appSettings.dbConnection,
     collection: appSettings.loggingCollection
   }
  );
  </code></pre>
  
  <p>This is the error I'm getting.</p>
  
  <pre><code>winston-mongodb: error initialising logger Error: invalid schema, expected mongodb
  </code></pre>
  
  <p>The host is the ip of a mongodb instance in azure, but that doesn't seem to be the issue because if I remove host (defaulting it to localhost according to the docs) and try to have it connect to my local mongo instance it gives the same error. It also doesn't seem to matter if I call any methods on the logger or not.</p>