save markdown file
edit markdown posts

usage:
  bb.sh edit article.md
to edit previously posted article (for which markdown source was saved),
and repost it (under the same name or not)
rename *.md file together with *.html

if called like this:
    bb.sh edit -n posted.md
then editing title will rename posted.html to reflect new title.
Now it will rename posted.md, too
use *.html file timestamp, even when editing *.md file
Merge pull request #39 from Lex-2008/save-md

Save md