learned from :
http://vimcasts.org/episodes/synchronizing-plugins-with-git-submodules-and-pathogen/

Installation:

    git clone https://github.com/Medusar/dotvim.git ~/.vim

Create symlinks:

    ln -s ~/.vim/vimrc ~/.vimrc
    ln -s ~/.vim/gvimrc ~/.gvimrc

Switch to the `~/.vim` directory, and fetch submodules:

    cd ~/.vim
    git submodule init
    git submodule update


to add a new plugin, for example, the https://draculatheme.com/vim/
	cd ~/.vim
	git submodule add [email protected]:dracula/vim.git bundle/dracula-theme

plugin list:

1. ack.vim
2. dracula-theme
3. vim-airline
4. nerdtree