Inconsistent release documentation

[gilmoreorless]

This repository is giving conflicting data about releases 0.5.28 and 0.5.29.

The new country-related methods (moment.tz.countries() and friends) are available from 0.5.28 onwards. This is currently the latest available published version on npm.

However, changelog.md says that these features were added in 0.5.29 (which hasn't yet been released). It has also missed version 0.5.27:

The releases page on GitHub says that it's both 0.5.28 and 0.5.29:

It's hard to tell which version these features are intended to be in, since the commit that updated the changelog (d7f687e) also includes feature changes that aren't mentioned.

[gilmoreorless]

Part of the changelog was fixed by #845. I've now corrected the release dates of a couple of others in 5162f1d.

I've also added git tags for 0.5.29 and 0.5.30 (as they were previously missing), and updated the Releases page to match.