A simple knitr report for displaying timelines of SurveyMonkey responses.
Download the data of interest into the statistical software format (it should
return a .zip), dump the zip into the same directory as the
response_timeline.rmd file, and fire off the generate_report.r script.
response_timeline.html should contain the result.
Multiple collectors are okay - each collector's results will be plotted in a different color.
