PyPI package name conflict

Turns out there is already a Python package named "gram":

```
[jeanthomas@computer gram]$ pip search gram
gram (0.2.1) - gram: GitHub Repo Account Manager
```

https://github.com/kawa-kokosowa/gram

Should we rename gram? Do messy things like naming the package `nmigen-gram`?

No files or tests are named. Start by checking the current PyPI/package metadata and the project's use of the name "gram"; compare the existing package conflict with possible alternatives such as "nmigen-gram". Done means reaching a naming decision and documenting the selected non-conflicting package name.

Written by the indexing model from the issue text.