some improvements to pandocNoLabel

ref: issue #121

Author: fmoralesc

syntax/pandoc.vim

@@ -239,7 +239,7 @@ else
     syn region pandocReferenceURL matchgroup=Operator start=/\]\@1<=(/ end=/)/ keepend display 
 endif
 " let's not consider "a [label] a" as a label, remove formatting - Note: breaks implicit links
-syn match pandocNoLabel /\]\@1<!\s\+\[[^\[\]]\{-}\]\s\+[\[(]\@!/ contains=pandocPCite
+syn match pandocNoLabel /\]\@1<!\(\s\+\|^\)\[[^\[\]]\{-}\]\(\s\+\|$\)[\[(]\@!/ contains=pandocPCite
 syn match pandocLinkTip /\s*".\{-}"/ contained containedin=pandocReferenceURL contains=@Spell display
 call s:WithConceal("image", 'syn match pandocImageIcon /!\[\@=/ display', 'conceal cchar='. s:cchars["image"]) 
 " }}}