Adds back arguments to Sequelize constructor for clarity (suggested by janmeier)

lib/sequelize.js

@@ -47,8 +47,9 @@ module.exports = (function() {
     @class Sequelize
     @constructor
   */
-  var Sequelize = function() {
-    var database, username, password, options = {}, urlParts
+  var Sequelize = function(database, username, password, options) {
+    var urlParts
+    options = options || {}
 
     if (arguments.length === 1) {
       urlParts = url.parse(arguments[0])