Support markdown as output

[boc-tothefuture]

Please consider adding support for markdown as an output format. This would allow people to use pickles to embed the pickles generated documentation within the same look and feel of their other documentation.

[ericcmmi]

There has been significant work done on the markdown format but it hasn't been pushed in a release yet. Will work on this. See this thread for further information on the current status of md support. #557 (comment)

[ericcmmi]

@boc-tothefuture I didn't realize that Dirk had pushed the work that had been done on the markdown format so it is available in the 2.21 release. Use Pickles.exe --documentation-format=markdown or Pickles.exe -df=markdown. I know it was only the initial attempt at implementing it so try it out when you have a chance and let us know if you have any suggested improvements.