Add info on how to prevent validation being added.

Closes #26

Author: ADmad

README.md

@@ -80,7 +80,11 @@ Slug comes with the following configuration options:
 - `unique:`: tells if slugs should be unique. Set this to a callable if you
  want to customize how unique slugs are generated. Defaults to `true`.
 - `scope`: extra conditions used when checking a slug for uniqueness.
-- `implementedEvents`: events this behavior listens to.
+- `implementedEvents`: events this behavior listens to. Defaults to
+  `['Model.buildValidator' => 'buildValidator', 'Model.beforeSave' => 'beforeSave']`.
+  By default the behavior adds validation for the `displayField` fields to make
+  them required on record creating. If you don't want these auto added validations
+  you can set `implementedEvents` to just `['Model.beforeSave' => 'beforeSave']`.
 - `onUpdate`: Boolean indicating whether slug should be updated when updating
   record, defaults to `false`.
 

src/Model/Behavior/SlugBehavior.php

@@ -35,7 +35,12 @@ class SlugBehavior extends Behavior
      * - unique: Tells if slugs should be unique. Set this to a callable if you
      *     want to customize how unique slugs are generated. Defaults to `true`.
      * - scope: Extra conditions used when checking a slug for uniqueness.
-     * - implementedEvents: Events this behavior listens to.
+     * - implementedEvents: Events this behavior listens to.  Defaults to
+     *    `['Model.buildValidator' => 'buildValidator', 'Model.beforeSave' => 'beforeSave']`.
+     *    By default the behavior adds validation for the `displayField` fields
+     *    to make them required on record creating. If you don't want these auto
+     *    added validations you can set `implementedEvents` to just
+     *    `['Model.beforeSave' => 'beforeSave']`.
      * - onUpdate: Boolean indicating whether slug should be updated when
      *   updating record, defaults to `false`.
      *