Tag 0.6.0?

[matthiasbeyer]

Same as #234 - there's a 0.6.0 release on crates.io, but the repository does not have a tag.

Please tag the release.

[CodingMarkus]

There's also no tag for 0.5.3.

[CodingMarkus]

In case some else cares as well and cannot wait for the tagging:

0.5.3 is 9c5a7ac
0.6.0 is 18eaf59