Use make-dir instead of mkdirp

[jonchurch]

This PR is meant to fix #139

This PR replaces mkdirp which doesn't seem to be maintained anymore with make-dir.

I realize that v2 of multer likely won't use storage engines at all, but maybe this can make it into v1.x.

All tests pass, and I don't believe this should be breaking for anyone, as it should function exactly the same as mkdirp did previously. make-dir was created to replace mkdirp.

I also added a test to make sure that a path is created when diskStorage is given a string for destination, as per the docs.

[jonchurch]

Aww heck, I didn't realize this uses async under the hood, so it will only work on Node >=8 😞

[LinusU]

Yeah, unfortunately this would be a breaking change, and thus we cannot add it to 1.x 😬

If you any other library we could use I'd be happy to consider it, but we cannot break compatibility with Node.js 0.10.0.

[jonchurch]

I tweeted at the maintainers of mkdirp to see if they'd consider a new release to fix this. Likely won't go anywhere, but figured I'd ask nicely.

I could publish something that fixes this, or we could roll our own, but I don't really think it's worth it.

[wesleytodd]

@isaacs do you think you could take a look at this? Looks like this is the result of https://github.com/substack/node-mkdirp/issues/70 not being resolved. Is there something we could do on this? Or is the correct move to use make-dir in 1.x and then move to node core fs.mkdir() recursive in 2.x? EDIT: re-read above and see that make-dir is not backwards compatible, so I guess the other option is to deprecate 1.x and get 2 out :P

[isaacs]

I think using make-dir is a reasonable approach. I've wanted to take some time to update mkdirp, but other things have taken precedence. I may get to it soon, but then again, I would've said that a few months ago, and here we are. I might also just scrap it and migrate to make-dir myself, because there are just other things too care about. And I believe substack is busy creating peer to peer maps of his tropical volcano island paradise.

[jonchurch]

For context, it looks like @isaacs forked mkdirp and published a new major to npm. That version supports >= 8.x same as make-dir. With multer v2 coming out soon, I don't think the linked issue will be fixed for v1.x.

[jonchurch]

I opened a PR w/ the fix for the issue this PR was attempting to circumvent on the newly maintained branch for the 0.x line of mkdirp. isaacs/node-mkdirp#15

So there's hope yet!