Squashed 'vim/custom/vim-yankstack/' content from commit cc49712

git-subtree-dir: vim/custom/vim-yankstack
git-subtree-split: cc4971236d5faca61c8a336bb2e52cefccbe3edc
Merge commit 'abeb33f289898113fc94bd6cae992ae6c1bbebfc' as 'vim/custom/vim-yankstack'
take off the training wheels