The new developers portal

I tried to download replays using the [replay API](https://github.com/Blizzard/s2client-proto/tree/master/samples/replay-api) that's being offered but it seems that, because of recent changes in Blizzard's developer portal, it's broken.

More specifically, I got the following error while trying to download replays from version 4.2.1 of SC2:

```
Traceback (most recent call last):
File "download_replays.py", line 124, in
main()
File "download_replays.py", line 84, in main
download_base_url = api.get_base_url()
File "download_replays.py", line 46, in get_base_url
return self.get(self.url("/data/sc2/archive_url/base_url"))["base_url"]
KeyError: 'base_url'
```

Start with the linked samples/replay-api and the download_replays.py entry point, especially get_base_url at the failing line. Reproduce the request for StarCraft II 4.2.1 and inspect the developer portal response. Done means the replay download flow handles the current response and completes without the missing base_url error.

Written by the indexing model from the issue text.