detailed user overview import

[Tschulie]

refering to google group entry: https://groups.google.com/forum/#!topic/formr/U0SSd6yvjFs

the following problem: importing data does not work with "rio::import()", only with "httr::content(httr::GET("https://formr.org/admin/run/STUDY/export_user_detail?format=csv"))"