Comply to Rust 0.12 warning about snake_case

```
more_pipes.rs:13:10: 13:26 warning: variable `fromParentSender` should have a snake case name such as `from_parent_sender`, #[warn(non_snake_case)] on by default
more_pipes.rs:13     let (fromParentSender, fromParentReceiver) = channel();
                          ^~~~~~~~~~~~~~~~
```