Switch to circe-config

[zakpatterson]

For consistency, we should use circe-config instead of pureconfig.

[pauljamescleary]

Is there an advantage to circe-config over pure-config? I am more-or-less curious as I haven't dived into a detailed comparison.

[zakpatterson]

I don't think there could be any measurable advantage, it just seems like a more natural choice for this project since we're already using circe. Also c-c doesn't do kebab-case like p-c does which seemed weird to me. Here's a line where I used it in another project, although we wouldn't need to use all the ApplicativeAsk complexity here:

https://github.com/clovellytech/http4s-modules/blob/master/db/src/main/scala/h4sm/db/config/package.scala#L21

[zakpatterson]

I went ahead and did it, let me know what you think.

[franklinchou]

This was closed by #123, no?

[zakpatterson]

Fixed with #123, thanks @franklinchou !