Add support for pxssh functionality of pexpect module.

[ChetanKolhe]

pxssh have good functionality which is very useful. like syn_original_prompt, set_unique_prompt .prompt..etc.

If possible any one can add those functionality ? All logic are available pxssh module of pexpect.

[fruch]

I'm not familiar with those features, and I'm not actively using this package anymore.

I would do my best to help pushing PRs for new features.