Rename package and CLI program to stravavis

[hugovk]

Also add a release checklist in RELEASING.md with the steps needed to upload to https://pypi.org/.

It also includes an optional step to upload to the testing https://test.pypi.org/ first.

You'll need to register accounts on each first.

The release process creates two files for upload:

• A so-called sdist or source distribution. This is a .tar.gz file and the minimum required.
• A "wheel", which allows for faster installation. More info: https://pythonwheels.com/