Update Vim 8 installation instructions

Author: sheerun

README.md

@@ -32,8 +32,7 @@ Optionally download one of the [releases](https://github.com/sheerun/vim-polyglo
 You can also use Vim 8 built-in package manager:
 
 ```
-" You should put in your ~/.vimrc "packadd vim-polyglot"
-git clone --depth 1 https://github.com/sheerun/vim-polyglot ~/.vim/pack/plugins/opt/vim-polyglot
+git clone --depth 1 https://github.com/sheerun/vim-polyglot ~/.vim/pack/plugins/start/vim-polyglot
 ```
 
 NOTE: Not all features of individual language packs are available. We strip them from functionality slowing vim startup (for example we ignore `plugins` folder that is loaded regardless of file type, instead we prefer `ftplugin` which is loaded lazily).