Before switching I used pathogen.vim for plugin management, which
resulted in a HUGE .gitmodules file as well as a huge directory
containing whole git repositories. vim-plug fixes all those problems. It
reduces the folder into a config file, containing one line per plugin
and also removes the need of adding those submodules to .gitmodules
Signed-off-by: Tobias Manske <tobias.manske@mailbox.org>