This PR also makes some changes to Travis CI's configuration file in an attempt to add testing on macOS, but reverts those changes. Getting macOS testing to work, especially with recent version of Python (3.8+), seems like it will be a more complicated undertaking than it might be worth.
Coverage remained the same at 94.283% when pulling 2a548e8229a2258928f6f9fab27006d4b0a255a9 on fix-macos into e40890b2b02aa0e25aa6ab82df90ddb33212cd19 on master.
This fixes #49. See 2a548e8.
This PR also makes some changes to Travis CI's configuration file in an attempt to add testing on macOS, but reverts those changes. Getting macOS testing to work, especially with recent version of Python (3.8+), seems like it will be a more complicated undertaking than it might be worth.