Add support for minio

[marcdeop]

I know of the existence of #345 but it hasn't been updated in a while and there have been some changes on master that make that pull request useless.

I tried using our minio instance as if it were and Amazon S3 endpoint ( adding a slight change to support a different endpoint than the defaults from Amazon) but the aws-sdk refused to work ( for some reason it still contacts Amazon to verify the credentials).

Thus, I ended up opting for adding full support for minio using https://github.com/minio/minio-js

I also noticed that there is an s3bucket config option which somehow I believe it belongs to the s3 section but I didn't dare to change that.

[SISheogorath]

Did you verify it works? I guess when it comes from @erasys it's running in production?

If so, can you please squash the commit messages together using git rebase -i HEAD~3 and provide one commit message that covers everything? (This makes it easier for you and us to keep the git tree in sync and the git history stays clean and short)

Thanks~

[marcdeop]

Thanks for checking this. We are indeed using it in our day to day work flow. However, I just realized that there was a minor change that I had to apply to our local setup, I will get back to you on this tomorrow evening ( European time)

[SISheogorath]

Please remove the unneeded semicolon to fix the linter warning: https://travis-ci.org/hackmdio/hackmd/jobs/267696722#L486

[marcdeop]

Fixed

[SISheogorath]

I was about to verify this setup and noticed that I have to think about how to set it up myself. Would it be possible to provide a little guide/documentation about how to setup minio with HackMD?

Something like what is Minio (very short), what do I need to do to set it up and what are example values for the config section.

I can probably figure it out, but not everyone is so familiar with these projects as you and me, so let's go for some docs 👍

Notice there is also an S3 guide in ./docs/guides/

[marcdeop]

We are quite busy with some deadlines at work but I hope I will have time for this next week :-)

I will get back to you then.

[SISheogorath]

Do you need help for the docs or can we make it land during the next week?

[SISheogorath]

Thanks for your work! I provide the docs after merging this.

Lots of thanks for this feature! Minio will allow people to have way better self-hosted experiences.