Use mozilla/http-observatory instead of dalf/http-observatory

[dalf]

dalf/http-observatory exists:

• to fix Different scoring between observatory.mozilla.org and the git repository mozilla/http-observatory#428
• to update the HSTS database : Automatic update of the *.json files. mozilla/http-observatory#431

Since yesterday, the next branch of mozilla/http-observatory contains a fix for the issue 428. The issue 431 is less important and the json files in dalf/http-observatory are no more updated (since travis stopped being free).

I don't know when the next branch is going to be merged into the master branch (replace or supersede).

Once done:

• we can use mozilla/http-observatory :

  searx-space/requirements-update.txt

  Line 1 in 624ee69

  httpobs @ git+https://github.com/dalf/http-observatory@master#egg=httpobs

• I can archive dalf/http-observatory

---

The API does seem to have changed:

• https://github.com/mozilla/http-observatory/blob/6ac246ad72d691fd2d0ac24b8ca8549631d87f7b/httpobs/scanner/local.py#L8

• searx-space/searxstats/fetcher/mozillaobs.py

  Line 20 in 624ee69

  result = scan(str(parsed_url.hostname), path=str(parsed_url.path), headers=DEFAULT_HEADERS)