Added docs for emitter.catch and changed the wording for the save docs a bit

lib/dao.js

@@ -390,12 +390,12 @@ module.exports = (function() {
   };
 
   /**
-   * Persist this instance to the database.
+   * Validate this instance, and if the validation passes, persist it to the database.
    *
-   * On success, the callback will be called with this instance. On validation error, the callback will be called with an Error instance. 
+   * On success, the callback will be called with this instance. On validation error, the callback will be called with an instance of `Sequelize.ValidationError`. 
    * This error will have a property for each of the fields for which validation failed, with the error message for that field.
    * 
-   * @param {Array} [fields] An optional array of strings, representing database columns. If fields is provided, only those columns will be saved.
+   * @param {Array} [fields] An optional array of strings, representing database columns. If fields is provided, only those columns will be validation and saved.
    * @param {Object} [options]
    * @param {Object} [options.fields] An alternative way of setting which fields should be persisted
    * @param {Transaction} [options.transaction]

lib/emitters/custom-event-emitter.js

@@ -253,6 +253,12 @@ module.exports = (function() {
     }).spread(onFulfilled, onRejected)
   }
 
+  /**
+   * Shorthand for `then(null, onRejected)`
+   *
+   * @param  {Function} onRejected
+   * @return {Bluebird.Promise}
+   */ 
   CustomEventEmitter.prototype.catch = function(onRejected) {
     return this.then(null, onRejected)
   }