Users can still set $HISTFILE if they want to and this will be used instead.
If no value is specified it will default to the $ZDIR/transient/history file.
This will prevent the double render issue that existed prior. It will still
render twice, but the second render will be defered until after tmux has been
quit.
At this point the following doesn't work.
- prompt
- history
- most autocomplete
Additionally with the tmux script getting loaded zplug we are getting a double
render issue, which is increasing the start up time. I'll probably move this
before the .zshrc set to short circuit having to set up all zplug script twice
before having a useable shell.
