Vagrantfile dynamically loads multiple vm configures

vagrant.md

##Vargantfile

```Ruby
# -*- mode: ruby -*-
# vi: set ft=ruby :

# Vagrantfile API/syntax version. Don't touch unless you know what you're doing!
VAGRANTFILE_API_VERSION = "2"

Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
  
  $config = config
  $project_name = File.basename(File.dirname(File.dirname(__FILE__)))

  config.vm.box = "ubuntu/trusty64"
  config.vm.synced_folder ".", "/vagrant", disabled: true

  config.ssh.forward_agent = true
  # HAX: fix ssh agent forwarding not being available during provisioning
  # see: https://github.com/mitchellh/vagrant/issues/1303
  config.vm.provision :shell do |shell|
      shell.inline = "touch $1 && chmod 0440 $1 && echo $2 > $1"
      shell.args = %q{/etc/sudoers.d/root_ssh_agent "Defaults    env_keep += \"SSH_AUTH_SOCK\""}
  end

  config.vm.provider "virtualbox" do |vb|
    # refer: https://www.virtualbox.org/manual/ch08.html#vboxmanage-modifyvm
    vb.customize [
      "modifyvm", :id,
      "--cpus", 2,
      "--memory", 1024,
    ]
  end

  Dir.glob("vm_*.rb").each { |vm_conf|
    unless File.directory?(vm_conf)
      load vm_conf
    end
  }

end
```

##settings.rb

```Ruby
module Settings
    ProjectName = File.basename(File.dirname(File.dirname(__FILE__)))
end
``` 

##vm configurations

* vm_web.rb

```Ruby
require_relative 'settings'

project_name = Settings::ProjectName

$config.vm.define "web" do |web|
    web.vm.hostname = "#{project_name}-web"
    web.vm.synced_folder ".", "/home/vagrant/#{project_name}"
    web.vm.network "private_network", ip: "192.168.21.10"
    web.vm.network "forwarded_port", guest: 8000, host: 8000
    web.vm.provider "virtualbox" do |vb|
      vb.name = "#{project_name}-web"
    end
end
```

* vm_db.rb

###...