trial_lists: Generate trial lists from a stimulus presentation lists
In dalejbarr/funfact: Functions for factorial experiments

Merge stimulus presentation lists with subject data to create a trial list.

1	trial_lists(design_args, subjects = NULL, seq_assign = FALSE)

`design_args`	Stimulus presentation lists (see `stim_lists`).
`subjects`	One of the following three: (1) an integer specifying the desired number of subjects (must be a multiple of number of stimulus lists); (2) a data frame with assignment information (must include a column `subj_id`); or (3) `NULL`, in which case there will be one subject per list.
`seq_assign`	If TRUE, assignment of subjects to lists will be sequential rather than random (default is FALSE)