- Added new model "SubscriberList"

- Added has_many_through relations to the new model + Subscriber model
- Added tests
- Fixed syntax in other models
This closes #95

lib/Models/SubscriberList.php

@@ -0,0 +1,35 @@
+<?php
+namespace MailPoet\Models;
+
+if(!defined('ABSPATH')) exit;
+
+class SubscriberList extends Model {
+  public static $_table = MP_LISTS_TABLE;
+
+  function __construct() {
+    parent::__construct();
+
+    $this->addValidations('name', array(
+      'required' => 'name_is_blank',
+      'isString' => 'name_is_not_string'
+    ));
+  }
+
+  public static function createOrUpdate($model) {
+    $exists = self::where('name', $model['name'])
+      ->find_one();
+
+    if($exists === false) {
+      $new_model = self::create();
+      $new_model->name = $model['name'];
+      return $new_model->save();
+    }
+
+    $exists->name = $model['name_updated'];
+    return $exists->save();
+  }
+
+  public function subscribers() {
+    return self::has_many_through(__NAMESPACE__ . '\Subscriber', __NAMESPACE__ . '\PivotSubscriberList', 'list_id', 'subscriber_id');
+  }
+}