Play nice with vimwiki. Fix #110

In order to use vim table mode over vimwiki native table formatting
support you need to add the following vimwiki settings to your vimrc :

```vim
let g:vimwiki_table_mappings=0
let g:vimwiki_table_auto_fmt=0
```

autoload/tablemode/table.vim

@@ -79,7 +79,7 @@ endfunction
 function! tablemode#table#GetCommentStart() "{{{2
   let cstring = &commentstring
   if tablemode#utils#strlen(cstring) > 0
-    return substitute(split(cstring, '%s')[0], '[^()]', '\\\0', 'g')
+    return substitute(split(cstring, '%s')[0], '[^(%)]', '\\\0', 'g')
   else
     return ''
   endif