wish: Add CHANGELOG.md

[markstos]

Thanks for this software.

It would useful to have a changelog to review so users can evaluate the differences between versions more easily when deciding whether or not to upgrade.

[markstos]

Ah, I see there are some updates notes in README. However, CHANGELOG.md (or HISTORY.md) is a more standard place to keep those notes. Also, it's important to include the /versions/ that changes corresponds to. People will be checking the version they have installed against the latest version to see what changed.

[nathanpeck]

Wish granted: I added changelog.md in version 0.5.0

Enjoy!