doc_file

Move your Rust crate's documentation into external files.

Why?

This is a proof of concept implementation of rust-lang/rust#15470. I hope to iron out questions and discover issues out of tree and then contribute this back to rustc itself.

Example usage

```rust

![feature(phase)]

// Paths are relative to the source file.

![doc(file="example_crate.markdown")]

[phase(plugin)] extern crate doc_file;

[doc(file="complicated_thing.markdown")]

pub struct ComplicatedThing;

/// Document other items like usual pub struct SimpleThing; ```