Headers should offer method to remove and return header

[untitaker]

If I take a Headers by value (moving it into my function), I want to avoid copying them. For that reason it would be useful if either Headers::remove would return the popped item (as HashMap::remove does), or if a new method was added.

[untitaker]

(I'm willing to write a PR for this)

[seanmonstar]

Hm, I agree with this entirely, 👍 . This would be a breaking change, since remove currently returns a bool, but it seems like the right one to make. As such, I'd aim it for master and not for the 0.9.x branch. Basically:

fn remove<H: Header>(&mut self) -> Option<H>;

[untitaker]

Great, I will write a PR as soon as possible.

[untitaker]

@seanmonstar Work in progress at #898, I underestimated the effort and need some guidance about further procedure.