fix ci and add CHANGELOG.me

[nikita-b]

• I added CHANGELOG.me
• I fixed CI: mkdocs doesn't support Python 2 anymore. The last supported version is 1.0.4. My suggestion is: let's release 1.4.2 (with /search and /var endpoints) and after release 2.0.0 where we'll drop Python 2 support.
• I removed Publish Test PyPi step because it doesn't work a lot of time and we can fix it later. But right now we need to have green CI :)
• Added all nomad versions.

[nikita-b]

@jrxFive @jonathanrcross Could we switch to the squash merge strategy?
History will be more clear and nice.
https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/configuring-pull-request-merges/configuring-commit-squashing-for-pull-requests

[jrxFive]

@nikita-b switched to squash by default. Next release would probably be more 1.5.0 than 1.4.2 I would think? Thanks for all the additions!