next, previous and current work for setext headers
Merge branch 'master' of git://github.com/plasticboy/vim-markdown into mappings
Header navigation mappings work for Setext headers.
Merge pull request #52 from cirosantilli/mappings

Header navigation mappings work for Setext headers.

Its been a month, and it seems it caused no problems to anyone, so I'm merging. If it breaks anything, I'll fix it =)