use version 1.0.0 with redmine 2.x (tested on 2.6.0 with custom reports plugin 0.1.4)
use version 2.0.0 with redmine 3.x (tested on 3.4.4 with custom reports plugin 0.1.5)
use version 3.0.0 with redmine 4.0.x (tested on 4.0.4 with a forked custom reports plugin)