Fixed the name of the Command Guide index.

llvm-svn: 9471
diff --git a/llvm/README.txt b/llvm/README.txt
index 430d415..af29732 100644
--- a/llvm/README.txt
+++ b/llvm/README.txt
@@ -64,7 +64,7 @@
         llvm/docs/GettingStarted.html
 
     LLVM Command Guide:
-        llvm/docs/CommandGuide/CommandGuide.html
+        llvm/docs/CommandGuide/index.html
 
     LLVM Assembly Language:
         llvm/docs/LangRef.html