Add support for maven classifier

[ghost]

For background, please see:

• https://gitter.im/typelevel/sbt-catalysts?at=5b3faf5903235c461fa3cc68
• https://github.com/typelevel/cats/pull/2312#issuecomment-403082086

.. integration with sbt-release would be great for Cats. (maybe a task to append the suffix? thus can be run as a release step command?)

Many thanks!

[Alistair-Johnson]

Hi...If anyone can give me some pointers on this, please, I might have a look at this.