Install brotli & zopfli using pip?

[bjuppa]

The instructions in the readme for installing brotli & zopfli with python3 may be outdated.

On my mac with python+pip installed via brew I just ran this to get it all installed:

npm install -g glyphhanger
pip3 install fonttools
pip3 install brotli
pip3 install zopfli

...so no need for me to clone and install them outside of pip. Actually the clone and install instruction may have done a python2 install when I first tried it so the packages were reported as not found when running glyphhanger with python3.

Should the readme be updated, or am I missing something? Perhaps this is mac/brew specific?