Shells for Rust

Wrapper around std::process::Command which make the use of Rust for shell scripting more appealing.

Documentation

http://proksima.github.io/shells-doc/shells/index.html

Simple example

```rust let (code, stdout, stderr) = sh!("echo '{} + {}' | bc", 1, 3);

asserteq!(code, 0); asserteq!(&stdout[..], "4"); assert_eq!(&stderr[..], ""); ```

A mnemotechnic to remember the ordering of the elements in the resulting tuple is the positions of stdout and stderr, they correspond to the standard streams numbers: 1 and 2 respectively.

If I a missing your favorite (at least partially) POSIX-compliant shell, submit a pull request!