Improve post stream

- Return all discussion post IDs from API requests which add/remove
posts, so the post stream updates appropriately. Related to #146
- Always unload posts that are two pages away, no matter how fast
you’re scrolling
- Retrieve posts from cache instead of reloading them
- Fix various bugs. Maybe #152, needs confirmation

src/Core/Posts/CommentPost.php

@@ -129,26 +129,6 @@ class CommentPost extends Post
         return $value;
     }
 
-    /**
-     * Define the relationship with the user who edited the post.
-     *
-     * @return \Illuminate\Database\Eloquent\Relations\BelongsTo
-     */
-    public function editUser()
-    {
-        return $this->belongsTo('Flarum\Core\Users\User', 'edit_user_id');
-    }
-
-    /**
-     * Define the relationship with the user who hid the post.
-     *
-     * @return \Illuminate\Database\Eloquent\Relations\BelongsTo
-     */
-    public function hideUser()
-    {
-        return $this->belongsTo('Flarum\Core\Users\User', 'hide_user_id');
-    }
-
     /**
      * Get text formatter instance.
      *