Use cascaded deletes

When we delete a user we should delete all the notes that belong to this
user including the revisions of these notes.

Signed-off-by: Sheogorath <sheogorath@shivering-isles.com>

lib/models/note.js

@@ -91,7 +91,9 @@ module.exports = function (sequelize, DataTypes) {
         Note.belongsTo(models.User, {
           foreignKey: 'ownerId',
           as: 'owner',
-          constraints: false
+          constraints: false,
+          onDelete: 'CASCADE',
+          hooks: true
         })
         Note.belongsTo(models.User, {
           foreignKey: 'lastchangeuserId',