implement ability to get index of trial relative to block
implement ability to get index of trial relative to block

adrianoesch/jsPsych,andyh616/jsPsych,erikasf/jsPsych,jspsych/jsPsych,andyh616/jsPsych,wolfgangwalther/jsPsych,vergenzt/jsPsych,shamrt/jsPsych,Scienthusiast/jsPsych,adrianoesch/jsPsych,erikasf/jsPsych,Scienthusiast/jsPsych,shamrt/jsPsych,jspsych/jsPsych,vergenzt/jsPsych,jspsych/jsPsych,jodeleeuw/jsPsych,wolfgangwalther/jsPsych,jspsych/jsPsych,msrresearch/jsPsych