Added vim-windowswap plugin to vimrc.
Added vim-windowswap plugin to vimrc.

- vim-windowswap swaps two windows while keeping the split layout
- added tmux-complete.vim, a deoplete.nvim completion source
  (not used yet)
- cleaned up vim-rtags settings

bfrg/dotfiles,bfrg/dotfiles,bfrg/dotfiles,bfrg/dotfiles