options.required does not work for inputType='checkbox'

[jasonlinapl]

options.required does not check if the form has a checked checkbox when options.required is specified, even though that is the expected behavior according to the docs (here)

[tiesont]

Looks like I missed adding any tests for the required option. I'll see what I can do over the weekend/next week.

[tiesont]

See #863 - will need to add tests. Will probably need a minor update to the code as well