Update runtime files

runtime/ftplugin/rst.vim

@@ -3,7 +3,7 @@
 " Maintainer: Marshall Ward <marshall.ward@gmail.com>
 " Original Maintainer: Nikolai Weibull <now@bitwi.se>
 " Website: https://github.com/marshallward/vim-restructuredtext
-" Latest Revision: 2018-01-07
+" Latest Revision: 2018-12-29
 
 if exists("b:did_ftplugin")
     finish
@@ -13,6 +13,11 @@ let b:did_ftplugin = 1
 let s:cpo_save = &cpo
 set cpo&vim
 
+"Disable folding
+if !exists('g:rst_fold_enabled')
+  let g:rst_fold_enabled = 0
+endif
+
 let b:undo_ftplugin = "setl com< cms< et< fo<"
 
 setlocal comments=fb:.. commentstring=..\ %s expandtab