Can't install via pip on OS X 10.11

[nathanielvirgo]

I'm unable to install via pip, and I don't think it's due to the issues that are mentioned on the troubleshooting page or #405 .

$ python3.6 -m pip install taichi
Collecting taichi
  Could not find a version that satisfies the requirement taichi (from versions: )
No matching distribution found for taichi

$ python3.7 -m pip install taichi
Collecting taichi
  Could not find a version that satisfies the requirement taichi (from versions: )
No matching distribution found for taichi

$ python3.8 -m pip install taichi
Defaulting to user installation because normal site-packages is not writeable
ERROR: Could not find a version that satisfies the requirement taichi (from versions: none)
ERROR: No matching distribution found for taichi

These are installed via macports, and I've checked they're all 64 bit.

I am running OS X 10.11. Could the old OS version cause this problem? (It's an old machine but it works well, so I don't want to rock the boat by upgrading the OS unless I have to.)

[thinking-tower]

@nathanielvirgo might be helpful to note that here, OS X (10.14+) is supported.

[nathanielvirgo]

Ah right, I'd managed to miss that. (It's in the table, but not in the list of requirements at the start of the "installation" section at https://github.com/taichi-dev/taichi.) I guess this can be closed, then. I'll be back if I take the plunge and upgrade the OS.

[thinking-tower]

@nathanielvirgo there's also 🐳  Docker 🐳   if it comes to it!