elm-upgrade doesn't work for 0.17 projects

[Andy]

I tried to auto upgrade an elm 0.17 project. It did work, because there is request to /new-packages which was removed. I'm not sure if this should have priority. This issue is for awareness and documentation. Maybe a paragraph to the README.md can be added, to explain how older elm projects are handled.

npx elm-upgrade@elm0.18.0                                                                                               1274ms
npx: installed 47 in 3.459s
{ HTTPError: Response code 404 (Not Found)
    at stream.catch.then.data (/home/as/.npm/_npx/6363/lib/node_modules/elm-upgrade/node_modules/got/index.js:123:13)
    at <anonymous>
    at process._tickCallback (internal/process/next_tick.js:188:7)
  message: 'Response code 404 (Not Found)',
  host: 'package.elm-lang.org',
  hostname: 'package.elm-lang.org',
  method: 'GET',
  path: '/new-packages',
  statusCode: 404,
  statusMessage: 'Not Found' }
ERROR: Unable to connect to http://package.elm-lang.org.  Please try again later.