Build a reading assignment: Generate an .Rmd file for a
reading assignment web page and PDF handout.
     
    
    Usage
    build_reading_assignment(schedule, date, cal_entry, semester)
 
     
    
    Arguments
- schedule
 
A schedule data frame.
 
- date
 
The reading due date.
 
- cal_entry
 
A calendar entry for the class.
 
- semester
 
A list of data for the semester, from the database.
 
 
    
    Value
    An updated schedule data frame