Warning when installing on OS X 10.12

[jpmedley]

Warning: You are using OS X 10.12.
We do not provide support for this pre-release version.
You may encounter build failures or other breakages.

If I find anything broken or failing, I'll add it to this ticket.

[surma]

Are you on macOS < 10.12? And how did you install simplehttp2server?

[jpmedley]

So,

• Installed homebrew to ~/Homebrew instead of the default location.
• I was prompted to upgrade xcode. The error went away.