Use rustyline crate for Input prompt

[jamesmcm]

The Input prompt has a few issues at the moment, mainly:

• There is no emacs/readline support and we'd have to handle each keypress manually to add it in
• Due to the above manual handling, some things like backspace in tmux don't work

We could use the rustyline crate underneath so we get all the readline functionality for free, and it should work in terminal multiplexers and cross-platform.

EDIT: Swapped liner for rustyline, as the former is dead.

[jamesmcm]

Hmm, I can't actually replicate the tmux backspace issues I had before now. It might have been due to pasting lines too maybe.

Nevertheless I think it would be useful to have the readline support, and also better handling for if the user pastes multiple lines (or if their paste ends with a newline, etc.)

[pksunkara]

Is this still an issue?

[jamesmcm]

I think it's still a good idea (and rustyline is still maintained) - ideally we could remove this whole loop if all the features work well (not sure if it has built-in history support though) - https://github.com/mitsuhiko/dialoguer/blob/master/src/prompts/input.rs#L262