title: Vagrant plugin command is not available when running `vagrant plugin install`
body: <p>I have tried installing vagrant from both an apt repo and gem but here's the output I am getting when I try to run <code>vagrant plugin install</code> (clearly no plugin command in output):</p>
  
  <pre><code>Usage: vagrant [-v] [-h] command [&lt;args&gt;]
  
      -v, --version                    Print the version and exit.
      -h, --help                       Print this help.
  
   Available subcommands:
       box
       destroy
       gem
       halt
       init
       package
       provision
       reload
       resume
       ssh
       ssh-config
       status
       suspend
       up
  </code></pre>
  
  <p>I have tried installing vagrant from both apt and Rubygems and in both cases I get no plugin command. I am running Ubuntu 12.04 LTS.</p>