Investigate pytest plugin, nose, and unittest integrations for easier use

[mmattb]

There may be some synergy in terms of e.g. outputting results in a shared format, test discovery, or others. I suspect people e.g. using Jenkins CI workflows and outputting in one of the special XML formats for test results could use some special wrappers, plugins, etc. for combtest. There may also be some pytest plugins that compliment this somehow.