Test fails on mac due to "Broken pipe"

[hibariya]

This issue has been extracted from #6. This error reproduces on v0.1.4.

it_can_hook_stdout_with_handler::it_can_hook_stdout_with_handler stdout ----
        thread 'it_can_hook_stdout_with_handler::it_can_hook_stdout_with_handler' panicked at 'called `Result::unwrap()` on an `Err` value: Io(Error { repr: Os { code: 32, message: "Broken pipe" } })', ../src/libcore/result.rs:837