I have used Clarify (http://www.clarify-it.com/) on an almost daily basis. I’ve tried lots of different screenshot programs and Clarify is really the best. If you’re looking for a rapid way to document anything with words and annotated images – then Clarify is your program. It exports to many different formats including Markdown. All of my tutorial posts that have images are done on Clarify. I can’t say enough good things about it.