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::new(|| { let termionbackend = backend::termion::Backend::init(); let bufferedbackend = cursivebufferedbackend::BufferedBackend::new(termionbackend); Box::new(bufferedbackend) });

```