Okay, so the fibers issue is related to it not liking the NVM installation of Node.
So on CentOS 7, the secret is to install the epe-release, then install nodejs. This installs Node v0.10.36, which is not what anyone wants. But once that is installed, you can go back to using NVM and a modern Node release and fibers is able to install!
So...yum -y install epel-release yum -y install nodejs npm install fibers