Properly publish v0.2.1 (and v0.2.0?) on github

[oisyn]

I just published 0.2.1 on crates.io. It includes the simplify_scale by @BeastLe9enD and simplify_with_locks API functions

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I think we should do a proper release on github, but I noticed that we haven't done that for 0.2.0 either. What do you think, should we just ignore 0.2.0 or still do that for history's sake? :)

Either way, we need a good summary of all the changes. Is the changelog complete?

[oisyn]

Oh shoot, I just realized I forgot to update the version number in readme.md