Always re-render prompt while navigating history

[amosbird]

#127

[AmokHuginnsson]

I need to think about more generic fix.
Proposed solution handles only very small subset of invalid behaviors when handling overlong lines.
It is quite possible that proper solution would go in completely different direction.
By proper solution I mean solution that handles multiline entries where there are more lines in entry than available lines on terminal and also some of those lines are (possibly much much) longer then width of the terminal.
In other words, proper solution would mean implementing a proper full screen text editor inside replxx.
I am not saying no to that and that is why I am hesitant to accept this pull request.

[amosbird]

Ok.. Maybe we can have this proper implementation gradually and in the meantime providing some temporary workaround, as #127 is indeed common and recurrent, which is a little bit inconvenient to user experience.