Dot release - v2.0.3.

Now I understand how I should've versioned my go module.

https://stackoverflow.com/questions/53344471/taking-a-repository-to-v2
explains how to change the module path when upgrading the major version.

This is for homebrew...

I messed up and merged a v2.0.0 tag that was a day old from another
branch... This meant github's 2.0.0 source archive was out of date,
which Ross discovered when building from the updated homebrew
formula. So this is a 2.0.1 version, and I will tag it accordingly.

Move these out of the top-level, to avoid clutter.

Ready for pushing to github!