This new validation didn't work correctly yet because of two reasons:

- When loading the wiki page in the `#update` controller action, the
  content in `attributes[:content]` won't be initialized which causes
  `content_changed?` to return true. Our factory on the other hand
  sets `attributes[:content]` as part of its initialization.

  We can fix this by using `raw_content` instead in `content_changed?`,
  and verify this in the specs by reloading the existing page from the
  wiki.

- Gollum converts CRLF line endings ("\r\n") to LFs ("\n"), so we also
  need to do this conversion in `WikiPage#content_changed?`.