Endian Trait Derivation

This provides a custom derive for the Endian trait on structs.

It currently only works on structs. Enums are not yet supported; I plan to look into this before a 1.0 release.

This crate is only useful as a sidekick to endian_trait.

```rust extern crate endian_trait;

[macro_use]

extern crate endiantraitderive;

[derive(Endian)]

struct Example { a: A, // others } ```