Add reference to Instance to public API

lib/sequelize.js

@@ -12,6 +12,7 @@ var url = require('url')
   , sequelizeErrors = require('./errors')
   , Promise = require('./promise')
   , Hooks = require('./hooks')
+  , Instance = require('./instance')
   , deprecatedSeen = {}
   , deprecated = function(message) {
     if (deprecatedSeen[message]) return;
@@ -245,6 +246,13 @@ module.exports = (function() {
   Sequelize.prototype.Transaction = Sequelize.Transaction = Transaction;
 
   /**
+   * A reference to the sequelize instance class.
+   * @property Instance
+   * @see {Instance}
+   */
+  Sequelize.prototype.Instance = Sequelize.Instance = Instance;
+
+  /**
    * Allow hooks to be defined on Sequelize + on sequelize instance as universal hooks to run on all models
    * and on Sequelize/sequelize methods e.g. Sequelize(), Sequelize#define()
    */