⚠️ Due to changes in OS X, Vagrant, and Virtualbox, this is no longer possible. 4/23/2016, JG
First, stop Apache. Apache listens on port 80. If it's running, Vagrant won't be able to bind a VM to listen on port 80.
Then, just add a forwarded port to your
config.vm.network "forwarded_port", guest: 80, host: 80
And boot up Vagrant as
sudo vagrant up