Bump version to 0.6.0

[lncrd]

I'd love to be able to use the *_of_slice variants without manually using patch.crates-io.

This PR updates murmur3 to version 0.6.0 for a new crates.io release.

Changes since the last release include adding non-copying implementations: https://github.com/stusmall/murmur3/compare/75a1128f95bb0d64e304646e453a6e18f831bebf..master