Fix inconsistency with tmux/vim understandings of vsplits
Fix inconsistency with tmux/vim understandings of vsplits

Vim thinks a vertical split is a split consisting of a vertical line
down the centre of the window to split.

Tmux thinks a vertical split is a split where resulting windows are
stacked vertically.

Note that these are opposite.

ouroboros8/dotfiles,ouroboros8/dotfiles