* Support \colorbox and \\fcolorbox
These are functions from the `color` package. They accept text, not math. They also have padding similar to `\fbox`.
Because of the padding, the code in `buildHTML` is intermixed with the `\fbox` code. I have not (yet) created a new file in the functions folder. This way, the reviewer gets a cleaner diff.
* Fix lint error
* colorbox screenshots
* Pick up review comments
