Adds authenticate to db.open if a username and password are set.

lib/adapters/mongodb.js

@@ -34,9 +34,21 @@ function MongoDB(s, schema, callback) {
     var server = new mongodb.Server(s.host, s.port, {});
     new mongodb.Db(s.database, server, {}).open(function (err, client) {
         if (err) throw err;
-        this.client = client;
-        schema.client = client;
-        callback();
+        
+        if (s.username && s.password) {
+            t = this;
+            client.authenticate(s.username, s.password, function(err, result) {
+              if (err) throw err;
+              t.client = client;
+              schema.client = client;
+              callback();
+            });
+            
+        } else {
+            this.client = client;
+            schema.client = client;
+            callback();
+        }
     }.bind(this));
 }