refactor: nerdtree repo has been moved to new place

.vimrc

@@ -136,7 +136,7 @@ Plug 'mileszs/ack.vim'
 Plug 'easymotion/vim-easymotion'
 Plug 'haya14busa/incsearch.vim'
 Plug 'jiangmiao/auto-pairs'
-Plug 'scrooloose/nerdtree'
+Plug 'preservim/nerdtree'
 Plug 'tiagofumo/vim-nerdtree-syntax-highlight'
 Plug 'Xuyuanp/nerdtree-git-plugin'
 Plug 'godlygeek/tabular'

README.md

@@ -364,7 +364,7 @@ This software is licensed under the [MIT license][75]. © 2016 chxuan
   [3]: https://brew.sh/
   [4]: https://github.com/junegunn/vim-plug
   [5]: https://github.com/Valloric/YouCompleteMe
-  [6]: https://github.com/scrooloose/nerdtree
+  [6]: https://github.com/preservim/nerdtree
   [8]: https://github.com/vim-airline/vim-airline
   [9]: https://github.com/powerline/powerline
   [10]: https://github.com/jiangmiao/auto-pairs

autoload/plug.vim

@@ -22,7 +22,7 @@
 "   Plug 'SirVer/ultisnips' | Plug 'honza/vim-snippets'
 "
 "   " On-demand loading
-"   Plug 'scrooloose/nerdtree', { 'on':  'NERDTreeToggle' }
+"   Plug 'preservim/nerdtree', { 'on':  'NERDTreeToggle' }
 "   Plug 'tpope/vim-fireplace', { 'for': 'clojure' }
 "
 "   " Using a non-master branch