Add versions, tags & --version cmd about augur HOT 3 CLOSED

I would recommend (naturally) the approach I took in https://github.com/nextstrain/cli:

• an augur/__version__.py that's simple enough to be statically parsed (for release management tooling)
• …but that can still be used to import a __version__ variable at runtime (for a --version option or version subcommand to use).
• setup.py then gets a snippet to read that file.

Does every push to master bump up the version?

No. The version should be managed manually and follow semantic versioning rules. Releases are things you version, not commits.

We should tag each version so that it's easy to checkout certain versions

Yes, totally. Here's what I did for nextstrain-cli: https://github.com/nextstrain/cli/blob/master/devel/release

augur --version should print the version

Yep, or augur version.

a changelog would also be a good idea at this point

Yes!

I think we start from 3.0.0

Sure.

from augur.

I endorse all of this.

from augur.

There's one bit of this that wasn't resolved by #210: a --version flag as an alias for augur version. I'll do that soon.

from augur.