[MERGE THIRD] Use smartdown version with markdown public API

Update smartdown version with the changes to the api - returning markdown instead of html.

We may want to hold off merging this and bump to 0.11.2 instead as that version has a couple of bug fixes (although I do not think they are manifested anywhere in smart-answers), we would need to create a separate version bump commit anyway)
no reason, I guess I probably spotted we already had an attr_reader down when I was adding the `markdown_to_html` function and thought to utilize it! I can make it neater in another PR