add: base64url support

[jrschumacher]

Using string replaceAll since base64 is external base64-js.
Dependency does not yet support base64url beatgammit/base64-js#53

[SamuelScheit]

I also need base64url encoding support for my project,
@jrschumacher thank you for implementing it, I'll use your branch until this PR gets merged.

[Dabada]

Any news for this ? Please.

[Hedzer]

same issue, any news?

[ChrisAntaki]

Thanks for coding this, @jrschumacher! Using it for a fork

[swetshaw]

I need base64url encoding support for my project, can we review and merge this ASAP?

[jrschumacher]

It's probably not going to happen if it's been this long. Just use my branch or just wrap the base64 function in a string replace.

[TDola]

Hopefully this is merged some day. It seems to work well
npm install feross/buffer#pull/314/head

[dcousens]

LGTM, I'll need to resolve the CI issues before I can merge though

[jrschumacher]

@dcousens I removed trailing spaces on line 955 of index.js

[jrschumacher]

@dcousens still interested in taking this?

[jrschumacher]

I rebased with the master branch and removed my lint scripts from the package.json to reduce conflicts.

[dcousens]

Thanks @jrschumacher, I'm happy to take this from here next I can, I need to check in on @chjj's pull request in #349, which might supersede this

[ST-DDT]

Would it be possible to merge and release this first since the other PR seems stuck for a long time now?