Extentions for Bincode (Binary Encoder / Decoder)

Example

```rust extern crate bincode; extern crate bincode_ext;

use bincodeext::byteorder::Le;

[derive(RustcEncodable, RustcDecodable, PartialEq)]

struct Foo { x: Le, // little endian y: u32, // big endian, due to defaults in bincode }