Fiona wheels for Python 3.8

Despite being busy with family stuff, I'm bringing blogging back tonight, and I'm also updating the project so that I can build manylinux1 and macosx wheels for Python 3.8. It's working great and there will be a Fiona 1.8.12 release on PyPI this morning. I'm going to regret this tomorrow when I have to get up at the crack of dawn to get kids to school, I'm sure, but it feels good to think about unblocking folks who want to try Fiona on 3.8.