Use Duration for timeouts

[nicos68]

I just found out about this lib. Thanks for working on it, it's helpful for my current project.

One thing bugs me : shouldn't the timeout() function accept stdlib's Duration as an argument ? From what I can see it only takes a From implementation to allow it, and I think it would make things much more explicit and consistent, and avoid errors.

If you agree I can do the PR.

[hoodie]

Hey, thanks for the input, that is an excellent point!
Please go right ahead!

[nicos68]

Done.