allow header after lines containing tags

fixes issue #108

also, fix regression about atx headers

Author: fmoralesc

syntax/pandoc.vim

@@ -308,10 +308,9 @@ call s:WithConceal("strikeout", 'syn match pandocStrikeoutMark /\~\~/ contained
 
 " Headers: {{{1
 "
-syn match pandocAtxHeader /\(\%^\|^\s*\n\)\@<=#\{1,6}.*\n/ contains=pandocEmphasis,pandocStrong,pandocNoFormatted,pandocLaTeXInlineMath,@Spell, display
+syn match pandocAtxHeader /\(\%^\|<.\+>.*\n\|^\s*\n\)\@<=#\{1,6}.*\n/ contains=pandocEmphasis,pandocStrong,pandocNoFormatted,pandocLaTeXInlineMath,@Spell, display
 syn match pandocAtxHeaderMark /\(^#\{1,6}\|\\\@<!#\+\(\s*.*$\)\@=\)/ contained containedin=pandocAtxHeader
-"call s:WithConceal("atx", 'syn match pandocAtxStart /#/ contained containedin=pandocAtxHeaderMark', 'conceal cchar='.s:cchars["atx"])
-syn match pandocAtxStart /#\+\s*/ contained containedin=pandocAtxHeaderMark conceal
+call s:WithConceal("atx", 'syn match pandocAtxStart /#/ contained containedin=pandocAtxHeaderMark', 'conceal cchar='.s:cchars["atx"])
 syn match pandocSetexHeader /^.\+\n[=]\+$/ contains=pandocEmphasis,pandocStrong,pandocNoFormatted,pandocLaTeXInlineMath,@Spell
 syn match pandocSetexHeader /^.\+\n[-]\+$/ contains=pandocEmphasis,pandocStrong,pandocNoFormatted,pandocLaTeXInlineMath,@Spell
 syn match pandocHeaderAttr /{.*}/ contained containedin=pandocAtxHeader,pandocSetexHeader