Automatically configure HISTFILE to preserve history

[Alveel]

The best fix is to explicitly configure HISTFILE. However (understandably) many users don't have this or know about this. This PR automatically configures HISTFILE to point to the original .zsh_history of the user instead of in the created tmp directory.

In lieu or accompanied with this, perhaps we can document the recommendation of setting HISTFILE?

I realise now I included #81 in my commit message but this fix only applies for zsh, not other shells.