Install phantomjs (http://phantomjs.org)
brew
has a recipe for phantomjs, but it has moved on to version 2.0.0, and we still require 1.8.2 (at newest), and we can't get that old and dirty with brew
anymore.
On a Mac:
mkdir -p ~/root
wget https://phantomjs.googlecode.com/files/phantomjs-1.8.2-macosx.zip -O ~/root/phantomjs-1.8.2-macosx.zip