title: Installing Amazon SDK via composer issue
body: <p>Good day:</p>
  
  <p>I'm running PHP 5.6 and I'm trying to install <code>aws/aws-sdk-php</code> however, getting error:</p>
  
  <pre><code>$ composer require aws/aws-sdk-php
  ./composer.json has been updated
  Loading composer repositories with package information
  Updating dependencies (including require-dev)
  Your requirements could not be resolved to an installable set of packages.
  
    Problem 1
      - symfony/translation v4.1.3 requires php ^7.1.3 -&gt; your PHP version (5.6.20) does not satisfy that requirement.
      - symfony/translation v4.1.3 requires php ^7.1.3 -&gt; your PHP version (5.6.20) does not satisfy that requirement.
      - Installation request for symfony/translation == 4.1.3.0 -&gt; satisfiable by symfony/translation[v4.1.3].
  
  
  Installation failed, reverting ./composer.json to its original content.
  </code></pre>
  
  <p>Not sure why I'm getting this issue as <code>aws/aws-sdk-php</code> requires minimum PHP 5.6 however, these dependencies requires php 7. I already have these dependencies installed in my <em>vendor</em> directory (through composer)</p>
  
  <pre><code>"require" : {
          "jenssegers/proxy" : "^2.2",
          "league/oauth2-client" : "0.12.1",
          "zendframework/zend-diactoros" : "^1.7",
          "nesbot/carbon" : "^1.22"
      }
  </code></pre>