Improve performance

[curusarn]

• The performance is an issue because whenever you run a shell command via bind -x ... the readline redraws the prompt which can be noticeable especially if you just hold down the keybinding.
• The whole thing is kind of a hack because of the limited way we can interact with readline and the command line content.
• Maybe we can improve the performance by handling vi mode and emacs mode separately because so far we are limited to escape codes that work for both modes.

[curusarn]

bash $READLINE_LINE is equivalent to zsh $BUFER and bash $READLINE_POINT is equivalent to zsh $CURSOR => 2 of the original bullet points are not valid anymore

[curusarn]

Hacks are no longer necessary => some of the performance issues are gone.

[curusarn]

GNU readline redraws prompt on every time a "widget" is executed. This is annoying and I messaged the mailing list about it.

[curusarn]

It's a design decision because GNU readline doesn't know what the executed widget is doing with the terminal. Performance is tolerable when your widget is really fast.