I honestly thought TOML (https://github.com/mojombo/toml - created by founder of Github) was a good configuration format. But unfortunately, I'm not sure that Tom has been a good steward of it and most of the interest in the early dies died off because Github issues would go unanswered or unresolved for months.
Same here. I have been keeping an eye on libucl[1] lately. The nginx-like config style seems very nice. I ran across it when looking at FreeBSD's pkg-ng (it uses it). I haven't seen any libs for it in any other languages yet though, so maybe it will end up being just another 'also ran'.