some simple methods

lib/sequelize/model-manager.js

+var ModelManager = module.exports = function() {
+  this.models = []
+}
+
+ModelManager.prototype.addModel = function(model) {
+  this.models.push(model)
+  return model
+}
+
+ModelManager.prototype.removeModel = function(model) {
+  this.models = this.models.filter(function(_model) {
+    return _model.name != model.name
+  })
+}
+
+ModelManager.prototype.__defineGetter__('all', function() {
+  return this.models
+})
\ No newline at end of file