Mongodb connection establishment update

Merge in pull request from original repo, cravall#105
Changed mongodb connection establishment to support newer driver and database versions of mongodb. The current authentication method (Db.authenticate) is deprecated (see log files). The new way to establish a connection is to use the MongoClient.

I create different connection strings, depending on whether a username is set or not. The way it is implemented only allows authentication against the selected database (i.e. no auth agains admin database when connecting to different db).

It should be tested whether the "encodeURIComponent" calls on the passwords are sufficient to prevent the connection uri from breaking on special character input.

src/lib/mongo.js

@@ -1,4 +1,4 @@
-var Db = require('mongodb').Db;
+var MongoClient = require('mongodb').MongoClient;
 var MongoServer = require('mongodb').Server;
 var async = require('async');
 var config = require('./config');
@@ -27,25 +27,17 @@ var getDb = function(host, done) {
     }
   }
 
-  var mongoDb = new Db(config.database, new MongoServer(host, config.mongoPort, mongoOptions));
-
-  mongoDb.open(function (err, db) {
+  var connectionURI;
+  if (config.username) {
+    connectionURI = `mongodb://${encodeURIComponent(config.username)}:${encodeURIComponent(config.password)}@${host}:${config.mongoPort}/${config.database}`;
+  } else {
+    connectionURI = `mongodb://${host}:${config.mongoPort}/${config.database}`;
+  }
+  MongoClient.connect(connectionURI, mongoOptions, function(err, db) {
     if (err) {
       return done(err);
     }
-
-    if(config.username) {
-        mongoDb.authenticate(config.username, config.password, function(err, result) {
-            if (err) {
-              return done(err);
-            }
-
-            return done(null, db);
-        });
-    } else {
-      return done(null, db);
-    }
-
+    return done(null, db);
   });
 };
 
@@ -214,4 +206,4 @@ module.exports = {
   initReplSet: initReplSet,
   addNewReplSetMembers: addNewReplSetMembers,
   isInReplSet: isInReplSet
-};
+};