cursivebufferedbackend

The buffering backend for any Cursive backend. Mainly it is created to address a flickering issue with Termion backend.

Inspired by the comment on the similar issue on Termion itself.

Usage

```rust let mut app = Cursive::trynew(|| { let crosstermbackend = backend::crossterm::Backend::init().unwrap(); let bufferedbackend = cursivebufferedbackend::BufferedBackend::new(crosstermbackend); Ok(Box::new(buffered_backend)) });

```