title: Composer does not download
body: <p>I installed composer and all works fine. When I run <code>composer -V</code> I just receive a warning about Xdebug.</p>
  
  <pre><code>You are running composer with xdebug enabled. This has a major impact on runtime performance. See https://getcomposer.org/xdebug
  Composer version 1.0-dev (4c0e163977f8289288df7b37e0fd0469d3e8cbc6) 2016-02-20 19:28:03
  </code></pre>
  
  <p>I tried to install Slim Framework with <code>composer require slim/slim "^3.0"</code> and receive the following error:</p>
  
  <pre><code>Loading composer repositories with package information                                                                               
    [Composer\Downloader\TransportException]                                     
    The "https://packagist.org/packages.json" file could not be downloaded: SSL  
    : Connection reset by peer                                                   
    Failed to enable crypto                                                      
    failed to open stream: operation failed
  </code></pre>
  
  <p>I was not sure, but thought the problem was the proxy, so I tried the solutions proposed <a href="https://stackoverflow.com/questions/17307600/php-composer-behind-http-proxy">here</a> and <a href="https://stackoverflow.com/questions/15268093/composer-cannot-download-files">here</a>.</p>
  
  <pre><code>export HTTP_PROXY="http://127.0.0.1:3128"
  export HTTP_PROXY_REQUEST_FULLURI=0 
  export HTTPS_PROXY_REQUEST_FULLURI=0
  </code></pre>
  
  <p>Still does not work. I also found <a href="https://github.com/composer/composer/issues/2041" rel="nofollow noreferrer">this closed issue</a> on GitHub, but anything works.</p>
  
  <p>Below are the result of <code>composer diag</code>:</p>
  
  <pre><code>You are running composer with xdebug enabled. This has a major impact on runtime performance. See https://getcomposer.org/xdebug
  Checking composer.json: FAIL
  No license specified, it is recommended to do so. For closed-source software you may use "proprietary" as license.
  Checking platform settings: FAIL
  The xdebug extension is loaded, this can slow down Composer a little.
   Disabling it when using Composer is recommended.
  
  Checking git settings: OK
  Checking http connectivity to packagist: FAIL
  [Composer\Downloader\TransportException] The "http://packagist.org/packages.json" file could not be downloaded (HTTP/1.1 502 Proxy Error ( The URL does not use a recognized protocol. There is no support for the protocol or application not )
  Checking https connectivity to packagist: FAIL
  [Composer\Downloader\TransportException] The "https://packagist.org/packages.json" file could not be downloaded: SSL: Connection reset by peer
  Failed to enable crypto
  failed to open stream: operation failed
  Checking HTTP proxy: FAIL
  [Composer\Downloader\TransportException] The "https://packagist.org/packages.json" file could not be downloaded: SSL: Connection reset by peer
  Failed to enable crypto
  failed to open stream: operation failed
  Checking HTTP proxy support for request_fulluri: FAIL
  Unable to assess the situation, maybe packagist.org is down (The "http://packagist.org/packages.json" file could not be downloaded (HTTP/1.1 502 Proxy Error ( O URL não usa um protocolo reconhecido. Não há suporte para o protocolo ou a solicitação não ))
  Checking HTTPS proxy support for request_fulluri: FAIL
  Unable to assess the situation, maybe github is down (The "https://api.github.com/repos/Seldaek/jsonlint/zipball/1.0.0" file could not be downloaded: SSL: Connection reset by peer
  Failed to enable crypto
  failed to open stream: operation failed)
  Checking github.com rate limit: FAIL
  [Composer\Downloader\TransportException] The "https://api.github.com/rate_limit" file could not be downloaded: SSL: Connection reset by peer
  Failed to enable crypto
  failed to open stream: operation failed
  Checking disk free space: OK
  Checking pubkeys: 
  Tags Public Key Fingerprint: 57815BA2 7E54DC31 7ECC7CC5 573090D0  87719BA6 8F3BB723 4E5D42D0 84A14642
  Dev Public Key Fingerprint: 4AC45767 E5EC2265 2F0C1167 CBBB8A2B  0C708369 153E328C AD90147D AFE50952
  OK
  Checking composer version: 
  
    [Composer\Downloader\TransportException]                                     
    The "https://getcomposer.org/version" file could not be downloaded: SSL: Co  
    nnection reset by peer                                                       
    Failed to enable crypto                                                      
    failed to open stream: operation failed                                      
  
  
  diagnose
  </code></pre>
  
  <p>Are there anything else that I can try?</p>
  
  <p>Notes:</p>
  
  <p>My OS is Ubuntu 14.04 and I'm using <a href="http://cntlm.sourceforge.net/" rel="nofollow noreferrer">CNTLM</a> to deal with a Windows proxy (TMG). Except composer, everything is working fine (browser,apt-get,npm...);</p>