v0.2.2

• Fix issues with coloring of groups in regexplain gadget when matched groups
  start and end at the same index, especially when there are zero-length
  groups (thanks, @HanOostdijk).

• Reduce package size by optimizing images and offloading the screencast gifs to
  the assets branch.

• Use of knitr is automatically detected when calling view_regex() inside
  an R Markdown document. The knitr parameter of view_regex() has been
  removed. Added result_only parameter for interactive viewing. As a side
  effect, the group coloring CSS is automatically embedded in the HTML output.