Merge pull request swirldev#599 from swirldev/dev

swirl 2.4.3

Merge pull request swirldev#497 from swirldev/dev

Update to 2.4.2

Delete .Rapp.history

Merge pull request swirldev#435 from swirldev/dev

Update master to 2.4.0

update NEWS for 2.2.21

increment version to 2.2.16

increment version for typo patch

add cran-comments.md to appease new devtools::release()

Merge pull request swirldev#162 from swirldev/regmods

Add regression models to recommended courses

bug fixes and slight version increment