PRs merged with pending work

[utensil]

This issue tracks some PRs merged with pending work:

• [ ] #9
• [ ] #34
• [ ] https://github.com/pygae/galgebra/pull/85#issuecomment-559809082
• [ ] #70 and https://github.com/pygae/galgebra/issues/28#issuecomment-558411574
• [ ] https://github.com/pygae/galgebra/pull/78#pullrequestreview-323373088
• [ ] https://github.com/pygae/galgebra/pull/37#issuecomment-566381357
• [x] #164 (pending work filed as #173)

or they will be buried in the pile of merged PRs.

[eric-wieser]

I'd recommend filing a new issue for each of these

[utensil]

I'll do that when I actually get to review the pending work and extract issues from them.