Update to config_v5.json format

[randycoulman]

We are using now the new config_v5.json format. There are some breaking changes in that (structure modified).

Originally posted by @laliconfigcat in #2 (comment)

[igorescobar]

@laliconfigcat could you give us some guidance on this one regarding on what to expect for this one?

[igorescobar]

Discussion: https://configcat-community.slack.com/archives/C01CN2YNWGK/p1603105539002700