H2O's documentation is built using Sphinx along with Dave Snider's excellent Read The Docs theme.
Xcode 5.1 seems to have broken CPython behavior on Mavericks. Here's how to install Sphinx:
Setting up easy_install, pip:
curl -O http://python-distribute.org/distribute_setup.py
sudo python distribute_setup.py
sudo rm distribute_setup.py
sudo easy_install pip
Setting up Sphinx:
export CFLAGS=-Qunused-arguments
export CPPFLAGS=-Qunused-arguments
sudo -E pip install Sphinx