Readline read_history and write_history addition

[Yitzchak Gale]

Judah Jacobson wrote:
> - readFile... writeFile...
> I think of readHistory and writeHistory as analogues to the above
> functions.

I don't think so. I don't really care about the file itself - that
just happens to be the way readline implements its persistence.
Non-existence of the file is the normal way that readline
represents the fact that there isn't any history yet.
The semantics of the API call are: load history, if any exists yet,
and report the result. Nothing exceptional about that.

> All that being said, this is a relatively minor issue

Agreed. All the more so with the MonadIO problem now factored
out.

Regards,
Yitz