Add Value::origin()

[matthiasbeyer]

Closes #97

[xuorig]

Hi @matthiasbeyer we're interested in using origin() in our code base, but it looks like it is not exposed in the latest release, even though 0.13.3 succeeds this PR. Any chance you would be willing to cut a new 0.13.x release soon?

[matthiasbeyer]

Yes, we had a bunch of changes that should be released I guess... at least the dependency updates, but also this change here.

I will publish 0.14.0 soonish (probably this evening, but feel free to ping me again if it didn't happen until sunday)! 😆

[xuorig]

Hi @matthiasbeyer, gentle ping on this 🙇

[matthiasbeyer]

Hah, well I guess sunday was a long time ago.
I hope we can get some stuff in (https://github.com/mehcode/config-rs/milestone/4) and I guess after that a release is really much overdue.

[polarathene]

I hope we can get some stuff in (https://github.com/mehcode/config-rs/milestone/4)

I should be addressing those by this weekend, just getting a good understanding with the MSRV + Cargo.lock / CI concerns being tackled elsewhere for 0.13.x first. Once I can chime in with my input on that, I'll get back to my own contributions 👍

[matthiasbeyer]

Awesome, thanks a lot for that!