Update to latest rust nightly.

- rustc 0.13.0-nightly (126db549b 2014-12-15 00:07:35 +0000)
Fix rustc warnings.
Change closures to FnMut to correspond to change in serialize crate.
serialize crate has moved out of tree to rustc-serialize.

See commit https://github.com/rust-lang/rust/commit/b04bc5cc49a398df712092a68ab9ad83019498ad
Update version to 0.0.3
Merge pull request #8 from crhino/rustc-62fb41c32

Update to newer rustc version