Revert "Allow overlap between response groups"
Revert "Allow overlap between response groups"

This reverts commit 3e1a05ab1932d0fe5077b4513a5044f9263dbe64.

shamrt/jsPsych,jodeleeuw/jsPsych,shamrt/jsPsych,jspsych/jsPsych,jspsych/jsPsych,jspsych/jsPsych,wolfgangwalther/jsPsych,wolfgangwalther/jsPsych,jspsych/jsPsych,msrresearch/jsPsych