John Hendy pointed out [1] that

list
- item1
- item2

Isn't the same as this:

list

- item1
- item2

when exported using the `md' backend (or its derivatives). But it needs to 
be to generate a proper document (at least with engines like pandoc.)

The attached patch enables this by adding a blank line after a 
`paragraph', but before a `plain-list' as long as the `paragraph' is not 
itself inside a list.

In other words, with the patch, the `md' export renders both lists with a 
blank line after the preceeding paragraph.

HTH,

Chuck

p.s. I have assigned copyright to FSF as `Charles Chester Berry' on Sept 
23, 2014 (RT: 945490).

Footnote [1]: http://thread.gmane.org/gmane.emacs.orgmode/92289