title: composer update -vvv is not working
body: <p>I have installed composer globally on ubuntu 14.04.
  When I run <strong>composer --version</strong> 
  it works with the following output</p>
  
  <pre><code>Composer version 1.0-dev (45b1f356c24d87788a339f6a50d6d78bef464c47) 2015-02-27 14:31:27
  </code></pre>
  
  <p>But when I run the following command
  <strong>composer update -vvv</strong></p>
  
  <p>It gives the following error</p>
  
  <pre><code>Failed to initialize global composer: Composer could not find the config file: /home/enamul/.composer/composer.json
  To initialize a project, please create a composer.json file as described in the http://getcomposer.org/ "Getting Started" section
  </code></pre>
  
  <p>I have no idea, why this is happening. Can anyone help me with that.</p>
  
  <p>Thanks</p>