Upgrade to 2.1.0

[wsargent]

This template is using Slick 2.0.2 and should be upgraded.

https://github.com/typesafehub/activator-hello-slick/blob/master/build.sbt#L10

[szeiger]

We have separate branches (and separte Activator template catalog entries pointing to them) for each major Slick version. The master branch is the "legacy" 2.0 version I hope we'll soon get support for switching between branches in Activator so that we can merge all the templates into a single multi-version template.