Bump tokio-codec from 0.1.0 to 0.1.2

Bumps [tokio-codec](https://github.com/tokio-rs/tokio) from 0.1.0 to 0.1.2.
- [Release notes](https://github.com/tokio-rs/tokio/releases)
- [Commits](tokio-rs/tokio@tokio-codec-0.1.0...0.1.2)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>