Update tutorials so Floki does not parse documents multiple times

[oltarasenko]

Based on:
https://elixirforum.com/t/web-scraping-tools/4823/31

Stop parsing each page four times.

When you run response.body |> Floki.find(...), you’re really running the equivalent of response.body |> Floki.parse() |> Floki.find(...) which means your four Floki.finds are parsing the whole document four times.

Instead, try parsed_body = Floki.parse(response.body) then parsed_body |> Floki.find(...).```

[philss]

For that I recommend that we start to use the newer functions Floki.parse_document/1 or Floki.parse_fragment/1.

They are functions that can return errors in case of something goes wrong with the parsing. Also, Floki.parse/1 is deprecated now.

TLDR:

with {:ok, parsed_body} <- Floki.parse_document(response.body) do
  # Floki.find(parsed_body, "a.foo") or something similar
end

[oltarasenko]

I think this issue is done now