Add Vagrant config and provisioning for CentOS 7

vagrant/centos-7-x64/Vagrantfile

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+# -*- mode: ruby -*-
+# vi: set ft=ruby :
+
+Vagrant.configure("2") do |config|
+
+  # Set which Vagrant "box" (base image) to use, and tell it how to set up the
+  # VM, packages to install, etc.
+  config.vm.box = "centos/7"
+  config.vm.provision :shell, path: "bootstrap.sh"
+
+  # Additional parameters for the VM
+  config.vm.provider "virtualbox" do |vb|
+      vb.memory = 2048
+      vb.cpus = 2
+  end
+
+  # Share the Phoenix/dist folder so the VM can get the source tarball and has
+  # a place to put the build results.
+  config.vm.synced_folder "../../dist", "/home/vagrant/dist"
+
+end

vagrant/centos-7-x64/bootstrap.sh

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+#!/bin/bash
+
+# Set up and update package repos
+yum -y install yum-utils
+yum -y install https://centos7.iuscommunity.org/ius-release.rpm
+yum -y update
+
+
+# Install necessary development and other packages
+yum -y group install development
+
+yum -y install gtk2 gtk2-devel gtk3 gtk3-devel \
+    webkitgtk webkitgtk-devel webkitgtk3 webkitgtk3-devel \
+    libjpeg-turbo-devel libpng-devel libtiff-devel \
+    SDL SDL-devel gstreamer gstreamer-devel gstreamer-plugins-base-devel \
+    freeglut freeglut-devel libnotify libnotify-devel
+
+
+# Install all available Python packages and their dev packages
+yum -y install python python-tools python-devel python-virtualenv
+yum -y install python34u python34u-tools python34u-devel
+yum -y install python35u python35u-tools python35u-devel
+
+
+# Set up virtual environments for each Python where the Phoenix builds will be done
+virtualenv --python=python2.7 Py27
+pyvenv-3.4 Py34
+pyvenv-3.5 Py35
+
+