update ruby and/or gems

[bodsch]

Currently, Smashing used many old ruby gems.
expectly rufus-scheduler in version 2.0.24. but this package is currently in version 3.4.2 available.

how can we plan a upgrade of modern ruby gem versions or ruby version too?

[olleolleolle]

When #65 is merged, things will be slightly newer.

The Travis CI matrix was just-now updated.

[terraboops]

Updated to 1.1.0 after merging some PRs.