sort_by() doesn't support wilson score or width

[nullforce]

sort_by() doesn't support wilson score or width.

These are the options indicated by the website:

<select name="sf" id="sf" class="input input--separate-left">
  <option value="created_at">Sort by creation date</option>
  <option value="score">Sort by score</option>
  <option selected="selected" value="wilson">Sort by Wilson score</option>
  <option value="relevance">Sort by relevance</option>
  <option value="width">Sort by width</option>
  <option value="height">Sort by height</option>
  <option value="comments">Sort by comments</option>
  <option value="random:9310657">Random!</option>
</select>

I'll submit a PR if I get a chance to determine the required edits.