Vagrant ALLOWED_HOSTS fixes for Django 1.6 upgrade.

Added code to define ALLOWED_HOSTS for Vagrant (192.168.56.4) and normal use (localhost, 127.0.0.1). Vagrant's makahiki_env.sh has been edited to add an environment variable, MACHINE_IS_VAGRANT, that is always true when makahiki_env.sh is copied to the user home directory by the bootstrap.sh script.