Motivation for this change

New version came out. Improved support for the prereleases of JUnit 5! And more https://blog.jetbrains.com/idea/2017/08/intellij-idea-2017-2-1-junit-5-rc2-spring-run-dashboard-and-its-faster/. Used it for a day and it seems to work fine.

Things done

Please check what applies. Note that these are not hard requirements but merely serve as information for reviewers.

• Tested using sandboxing
  (nix.useSandbox on NixOS,
  or option build-use-sandbox in nix.conf
  on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • Linux
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.