Update README. Fixes #24

Author: benmills

README.mkd

@@ -16,6 +16,8 @@ With **[vim-bundle](https://github.com/benmills/vim-bundle)**: `vim-bundle insta
 
 Otherwise download the latest [tarball](https://github.com/benmills/vimux/tarball/master), extract it and move `plugin/vimux.vim` inside `~/.vim/plugin`. If you're using [pathogen](https://github.com/tpope/vim-pathogen), then move the entire folder extracted from the tarball into `~/.vim/bundle`.
 
+_Note:_ Vimux requires vim with compiled ruby support. You can confirm you have ruby support by running `vim --version | grep +ruby`.
+
 ## Platform-specific Plugins
 
 * [vimux-ruby-test](https://github.com/pgr0ss/vimux-ruby-test) a set of commands to easily run ruby tests