Remove Chronic Duration dependency

[Juanmcuello]

Chronic Duration depends on numerizer ~> 0.1.1, so is not possible to update to latest version (0.2.0).

A possible solution could be to update numerizer to 0.2.0, but last commit was 9 years ago, so I think that maybe a better approach could be to remove that dependency entirely.

It seems to be used in the web views to express the different times intervals, but I see Sidekiq already has some methods to help with that, although not sure if all that are needed here.

I'm wondering if removing this dependency if something you are open to.