Remove the vim configuration files from the repository. I have moved fully over
to neovim and so these configuration files have stagnated. Instead, let's symlink the
neovim config for vim
* remove vim/
* add symlinking code in install/link.sh to symlink neovim config for vim
* symlink config/nvim -> ~/.vim
* symlink config/nvim/init.vim -> ~/.vimrc
* Remove old/outdated info from README
* Revise Vim and Neovim section of README
* move ~/.nvim to ~/.config/nvim
* move ~/.nvimrc to ~/.config/nvim/init.vim
* update install/link.sh to skip already existing files
* update install/link.sh to handle creating symlinks for files in newly created config/ directory
These changes are consistent with the latest neovim install, which moves away from ~/.nvim and ~/.nvimrc
