Update the-phlow to be used with zenhub board

[lakruzz]

A few things have changed since we stopped using Waffle and started using Zenboard.

• [x] We don't use briefing anymore. Instead we mark the issue as an epic in ZB
• [x] We don't use the T-shirt sizes anymore, instead we use the estimates provided in the ZB
• [x] Except "Too big" which still makes since (larger than 8)
• [x] The status markers to do, in progressand up next don't control the flow anymore - it's implemented differently in ZB