Fixes Compatibility with Scala 2.10

[juanpedromoreno]

This PR fixes/adds:

• Adds scala 2.10 to the travis file to run the tests for this scala version.
• Fixes compatibility with Scala 2.10 adding the paradise compiler plugin (needed when using with the kind-projector and Scala 2.10).
• Fixes docs (divergence implicits issue) for Scala 2.10 with -Xdivergence211 compiler flag.
• Upgrades sbt-catalysts-extras, squeezing all the plugin dependencies into a single one.
• Cats, kind-projector, monix and scalatest dependencies are using the same versions as before, but in this case, through the sbt-catalysts-extras plugin.

Please, @dialelo @raulraja could you review? Thanks!

[raulraja]

LGTM! /cc @adelbertc

[adelbertc]

Hurrah!