vim: Auto-install Plug if required

vimrc

@@ -1,5 +1,11 @@
 " Adapted from Dan's .vimrc, and Sven Gucke's vimrc.forall - Paul
 
+if empty(glob('~/.vim/autoload/plug.vim'))
+  silent !curl -fLo ~/.vim/autoload/plug.vim --create-dirs
+          \ https://raw.githubusercontent.com/junegunn/vim-plug/master/plug.vim
+  autocmd VimEnter * PlugInstall --sync | source $MYVIMRC
+endif
+
 call plug#begin('~/.vim/plugged')
     Plug 'junegunn/vim-easy-align/'
     Plug 'junegunn/fzf', { 'dir': '~/.fzf', 'do': './install --all' }