Document PriorityQueue.

[treeman]

Add examples to methods.

[steveklabnik]

"This will be a max-heap."

[steveklabnik]

Thanks so much for all of this, this is great. :) One small stylistic note: you can use vec![] as well as vec!(), and I think it's slightly preferred, since it looks a bit more like [T]. Not 100% sure on that, though.

[sinistersnare]

+1 on vec![] instead of vec!()

[treeman]

I do like vec![] more. vec!() is used practically everywhere in the code and other documentation (Vec for example), but that might be the old style. Which we probably should change I gather?

[treeman]

Made a change at Vec doc to reflect vec![] style: #15894

[huonw]

"This preallocates enough memory for capacity elements, so that the PriorityQueue does not have to be reallocated until it contains at least that many values."

[treeman]

Thanks, this is much better.

[brson]

Needs rebase.

[huonw]

r=me with that rebase (and possibly squashing the last 4 commits into a single one).

[treeman]

Rebased and squashed.