Fix to restore bindings after switching to vi-mode

the vi-mode plugin destroys any bindings made before it is sourced due to the
'bindkey -v' call to switch to using vi-mode.  This patch saves the bindings
before invoking 'bindkey -v' then rebinds them afterwards, this fixes a number
of outstanding issues due to people using vi-mode and having things in oh-my-zsh
break due to the bindings being destroyed