`codecov.io` and code-coverage measurements of python code in this repository

[ilaflott]

We have pylint and a pylintrc, great!

we're migrating code out where we can and into fre-cli, great, great great!

some of the code in this repo is covered by unit tests, but not all, which ones? we don't know, because we don't have coverage measurements.

this issue is to track which parts have coverage measurements and which do not.