Updated runtime files.

runtime/syntax/rmd.vim

@@ -1,15 +1,13 @@
 " markdown Text with R statements
 " Language: markdown with R code chunks
-" Last Change: Wed Jul 09, 2014  10:29PM
+" Homepage: https://github.com/jalvesaq/R-Vim-runtime
+" Last Change: Sat Feb 06, 2016  06:45AM
 "
 " CONFIGURATION:
 "   To highlight chunk headers as R code, put in your vimrc:
 "   let rmd_syn_hl_chunk = 1
 
-" for portability
-if version < 600
-  syntax clear
-elseif exists("b:current_syntax")
+if exists("b:current_syntax")
   finish
 endif
 
@@ -58,6 +56,8 @@ if rmdIsPandoc == 0
   if exists("b:current_syntax")
     unlet b:current_syntax
   endif
+  " Extend cluster
+  syn cluster texMathZoneGroup add=rmdrInline
   " Inline
   syntax match rmdLaTeXInlDelim "\$"
   syntax match rmdLaTeXInlDelim "\\\$"