closes #82 Also added a `HISTFILE` so it always reads the correct file that the shell is pointing to Is there a `HISTFILE`? If so, use it If it's Zsh: Is there a `ZDOTDIR`? Use `ZDOTDIR/.zsh_history` If it's Fish: Is there an `XDG_DATA_HOME`? Use `XDG_DATA_HOME/fish/fish_history` If none of them are present, revert to the default `$HOME/...`