backout b2f301f73c
backout b2f301f73c

Backout commit b2f301f73c

First of all, it caused flicker (which is caused by a Vim bug:
https://groups.google.com/d/msg/vim_dev/fdgPqmYZwOk/KJzR4l9wAwAJA)

and then the cache was not reset when editing a new file.

So let's just revert that commit, although it does affect performance.

fixes #1499

bling/vim-airline,tschundler/dotfiles,tschundler/dotfiles,yzhou61/vim-airline,tschundler/dotfiles,unphased/vim-airline,rchicoli/vim-airline,chrisbra/vim-airline