add support for txt2tags

doc/NERD_commenter.txt

@@ -806,9 +806,9 @@ if your face looked like a toaster and a t-rex put together? :(
       - the default mappings now start with <leader>c instead of ,c
       - see :help NERDComMappings, and :help NERDCreateDefaultMappings for
         more info
-    - add support for applescript, calbire, man, SVNcommit and potwiki. Thanks
-      to nicothakis, timberke, sgronblo, mntnoe, Bernhard Grotz and John
-      O'Shea respectively.
+    - add support for applescript, calbire, man, SVNcommit, potwiki, txt2tags.
+      Thanks to nicothakis, timberke, sgronblo, mntnoe, Bernhard Grotz, John
+      O'Shea and François respectively.
     - bugfix for haskell delimiters. Thanks to mntnoe.
 2.1.18
     - add support for llvm. Thanks to nicothakis.
@@ -1025,6 +1025,7 @@ Jerónimo Carballo                   stata
 Phillip Kovalev                     xquery
 Bernhard Grotz                      potwiki
 sgronblo                            man
+François                            txt2tags
 
 ==============================================================================
 9. License                                                    *NERDComLicense*

plugin/NERD_commenter.vim

@@ -811,6 +811,8 @@ function s:SetUpForNewFiletype(filetype, forceReset)
         call s:MapDelimiters('#', '')
     elseif a:filetype == "tssgm"
         call s:MapDelimiters("comment = '","'")
+    elseif a:filetype == "txt2tags"
+        call s:MapDelimiters('%','')
     elseif a:filetype == "uc"
         call s:MapDelimitersWithAlternative('//','', '/*','*/')
     elseif a:filetype == "uil"