write_into

Defines a trait built on top of io::Write to write things into it.

Example

```rust use writeinto::{BigEndian, WriteInto, writeinto};

let mut buffer = Vec::new(); writeinto(&mut buffer, BigEndian(0xCAFEBABEu32)).unwrap(); asserteq!(&buffer, &[0xCA, 0xFE, 0xBA, 0xBE]); ```