Upgrade Cats version

[Daniel Shuy]

Validation depends on Cats 0.6.0. The latest Cats version (at time of writing) is 0.9.0.

This is a major roadblock to using to using this library, as many other libraries depend on newer versions of Cats, causing incompatibilities among library dependencies.

[Julien Tournay]

Hi Daniel,

I just published validation 2.1.0. It's available for Scala 2.11.8 and 2.12.2. The cats version is 0.9.0.
Enjoy :)

[Daniel Shuy]

Wow, thanks so much!

I just want to say that this is such a great library. It is the main reason for me to use ScalaJS CrossProjects :)