Add message on how to view changelog after Update.

If no errors exist, the status-line will inform users how to view the
Changelog after BundleUpdate! is completed.

autoload/vundle/installer.vim

@@ -29,6 +29,10 @@ func! s:process(bang, cmd)
       let msg = 'With errors; press l to view log'
     endif
 
+    if 'updated' == g:vundle_last_status && empty(msg)
+      let msg = 'Bundles updated; press u to view changelog'
+    endif
+
     " goto next one
     exec ':+1'