Update README.

List can be manualy updated for now :

1. Download adaway host file https://adaway.org/hosts.txt

2. Download Exodus trackers file https://reports.exodus-privacy.eu.org/api/trackers

3. Open build_list.html in a Firefox.

4. When the browser finished computing, copy past the page content in the list/e_trackers.json file.

5. Commit this new file version.

1. build a new list : 

```

   $ node build_list.js 

   Starting list update

   adaway OK

   exodus OK

   enrich exodus OK

   Trackers list finished

   DONE

```

2. Chech validity of the list :

```

$ node validate_json.js 

JSON format is as expected

```

3. Commit the just generated version of list/e_trackers.json