Update ruby version and gems

[tbjoern]

Its been a long time since the project was created. The ruby version and gems are outdated.
They have been updated in the update_ruby_and_gems branch.

Noteable changes and findings:
FactoryGirl was replaced with FactoryBot
FactoryBot.attributes_for(:model, attribute: value) will not incorporate the attribute: value pair in the result hash.

TODOs:

• search for instances of attributes_for and check if the tests using it work as intended.
• merge current dev