Creat system for regularly regenerating solutions with newest R/packages

[ethanwhite]

What is the problem?

Currently the output solutions are generated once and then typically only changed if the associated exercise is changed. But changes in defaults in R and packages change the details of how the results are displayed. This is confusing to students.

So, we need to automatically regenerated solutions periodically with up-to-date versions of everything.

This should be done in concert with switching over to readr for all data reading to improve how data frames are output.

Location of problem (optional)

No response

[ethanwhite]

Implemented over in https://github.com/weecology/dcsem-solutions/