Enhance peek_data functionality
- If two calls to peek_data are defined, make the second to take the data from the first and plot it as comparator (e.g. in red lying under new peek data in black)
- find peek points by centering on points of maximum amplitude (suitably separated from other peeks), e.g.
- peek i = window around max(all_data)
- remove peek i window from data
- repeat
- plot ERPimage from all data if user supplies epoching event