Delete this repository and use upstream when 1.16 drops

[afirth]

Expected Behavior

We use upstream viper

Actual Behavior

We forked viper to allow sub inheritance, so that we can use env vars to override config values

Additional Information

Similar commits were introduced in spf13#1056 and finally dropped. The next release of viper will hopefully include 3f44490 and 3970ad1 and at that point we should switch back to upstream and archive this repo

[afirth]

cc @FATMAP/gophers

[afirth]

it's done!