Add link to automatic installation instructions

Close #711

Author: junegunn

README.md

@@ -36,6 +36,11 @@ curl -fLo ~/.vim/autoload/plug.vim --create-dirs \
     https://raw.githubusercontent.com/junegunn/vim-plug/master/plug.vim
 ```
 
+You can automate the process by putting the command in your Vim configuration
+file as suggested [here][auto].
+
+[auto]: https://github.com/junegunn/vim-plug/wiki/tips#automatic-installation
+
 ###### Windows (PowerShell)
 
 ```powershell