Integration with fm-sbt-s3-resolver

[coltfred]

https://github.com/frugalmechanic/fm-sbt-s3-resolver writes to an s3 bucket as a maven repo. Would you be interested in supporting the s3:// urls? This would allow people who are publishing to a private maven repo on s3 to use your plugin.

I think I have a pretty good idea of how that should be done, but didn't want to do the work if you weren't interested in supporting it.

Thanks!

[rtimush]

Hi @coltfred. I think it could be a good addition for those who use the S3 resolver, so a pull request will be very welcome! Just make sure that you don't pull an aws sdk as a dependency for everyone :-)