Updated history to escape history entries differently

[fdncred]

@gwenn How's this for a fix for #409?

I used the snailquote escaping/unescaping crate found here

I tested it with nushell and it seemed to work, once I straightened out my history.txt file

[fdncred]

There is an unwrap() in there because I wasn't sure what else to do.

[gwenn]

Thanks for your PR but:

• The only thing we want is to make the distinction between single-line and multi-lines entry in history.
  To do so we need to escape '\n'.
  But we have to also escape '\' to avoid ambiguity.
  And that's all !
• We may also need to timestamp entries for history left in broken state #400.
  So it seems wise to implement our own "parser" which should help supporting new format(s).

See #412.

[fdncred]

@gwenn Ok. Looks good to me. Thanks for putting my test in there.