improve tracking of participation

maybe a spreadsheet
https://docs.google.com/spreadsheets/d/1IW9jGxFdritRrdcU07qXh3awEmp4vmBTUc1ayWhFqYA/edit#gid=0

or labels: https://github.com/kalamuna/playbox/labels

but def better reporting is needed. added #5 to https://kalamuna.atlassian.net/wiki/display/HR/Playbox+Product+Owner
