Finish fixing #17

[GarkGarcia]

This is a follow up from #17.

I messed something up while trying to pull some changes from upstream, so there are 23 commits from my previous contribution in here.

The only relevants commits are the last two.

---

This change is 

[jonhoo]

Ah, yes, that's my fault because I ended up doing some squashing. If only the last two matter, run:

$ git remote add upstream https://github.com/jonhoo/flurry.git
$ git fetch upstream
$ git rebase --onto upstream/master HEAD~2

That should, in theory, replay just the last two commits onto the current master branch. Then you'll have to do:

$ git push --force-with-lease

To overwrite your current PR branch with the rebased one.

BTW, if you want to learn more about this sort of magic, I highly recommend this lecture.

[jonhoo]

@GarkGarcia I just pushed a commit to master that re-aligns the methods in map_ref.rs with those in map.rs to make comparison easier. We should probably do the same here for set.rs. I've also added a newline above each "See also ..." line, so that it doesn't get lost in the surrounding text in the docs.

[GarkGarcia]

We should probably think about implementing HashSet::intersection, HashSet::union and HashSet::difference equivalents.

[jonhoo]

@GarkGarcia Let's leave those for later so that we do not overload this PR too much.

[GarkGarcia]

@GarkGarcia Let's leave those for later so that we do not overload this PR too much.

Fair enough.

[jonhoo]

Okay, so, apparently I can't push directly to your branch, but I pushed the added commits to pr-17-augment. You should be able to merge my commits using:

$ git fetch upstream
$ git merge upstream/pr-17-augment

[jonhoo]

LGTM 👍

[jonhoo]

@GarkGarcia In a follow-up PR, it'd be great to also add a test suite for the ref version of set (just like we have one for map)

[GarkGarcia]

@GarkGarcia In a follow-up PR, it'd be great to also add a test suite for the ref version of set (just like we have one for map)

Makes sense. We could probably include the tests in a PR for #20?