Updates chalk to 0.5.x

Updates [Chalk](https://www.npmjs.org/package/chalk) to latest version, .

Amongst other chances this version performs about *60 times faster*, so upgrading may increasing logging performance. For a full list of chances, see the [release notes](https://github.com/sindresorhus/chalk/releases/tag/v0.5.0).

This version should be fully backwards compatible, and introduce no breaking chances.
Merge pull request #23 from jbnicolai/update-chalk

Updates chalk to 0.5.x