Since the vim plugins are stored in submodules and vim-plug is not a big
fan of that when installing (Needs PlugClean and PlugInstall again
although the repos of the plugins were already pulled) it makes more
sense to me to use vim8s native plugin management.
Use vim-plug to load onedark instead of the two files in
vim/{autoload,colors}. This enables to update the theme and have it as a
submodule in the rep.
Replace the zsh-history-substring-search plugin with fzf by adding a
function that starts the fzf-history-widget when pressing <Up> with a
nonempty BUFFER. The widget then uses the buffer automatically as query
for fzf.
