Add link to the active fork & transfer gem ownership?

[rathboma]

Hey @krobertson,

Looks like there's an active fork at https://github.com/deb-s3/deb-s3

Hoping you can:

1. Simply add the link to the readme?
2. Transfer gem ownership to the new repo maintainers?

Thanks!

[rathboma]

@krobertson if you have 2 mins, this would be super helpful to lots of folks!