Backport data types under DataTypes namespace to v3.

lib/sequelize.js

@@ -300,6 +300,12 @@ Sequelize.prototype.Validator = Sequelize.Validator = require('validator');
 
 Sequelize.prototype.Model = Sequelize.Model = Model;
 
+/**
+ * A reference to the sequelize class holding commonly used data types. The datatypes are used when defining a new model using `sequelize.define`
+ * @property DataTypes
+ */
+Sequelize.DataTypes = DataTypes;
+
 for (var dataType in DataTypes) {
   Sequelize[dataType] = DataTypes[dataType];
 }