Prepare release 8.4.0

Closes MyIntervals#345, MyIntervals#338

Merge tag '8.2.1' into drop-eval

* tag '8.2.1':
  Don’t use eval

Merge tag '8.1.1' into drop-eval

* tag '8.1.1':
  Don’t use eval

Merge tag '8.0.1' into drop-eval

* tag '8.0.1':
  Don’t use eval

Merge tag '7.0.4' into drop-eval

* tag '7.0.4':
  Don’t use eval

Merge tag '6.0.2' into drop-eval

* tag '6.0.2':
  Don’t use eval

Merge tag '5.2.1' into drop-eval

* tag '5.2.1':
  Don’t use eval

Merge tag '5.1.3' into drop-eval

* tag '5.1.3':
  Don’t use eval

Merge tag '5.0.9' into drop-eval

* tag '5.0.9':
  Don’t use eval

Merge tag '4.0.1' into drop-eval

* tag '4.0.1':
  Don’t use eval