title: couldn't install sonata admin bundle
body: <p>while installing admin bundle through this error : </p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>Your requirements could not be resolved to an installable set of packages.
  
    Problem 1
      - sonata-project/admin-bundle 2.3.7 requires sensio/generator-bundle ~2.3 -&gt; no matching package found.
      - sonata-project/admin-bundle 2.3.6 requires sensio/generator-bundle ~2.3 -&gt; no matching package found.
      - sonata-project/admin-bundle 2.3.5 requires sensio/generator-bundle ~2.3 -&gt; no matching package found.
      - sonata-project/admin-bundle 2.3.4 requires sensio/generator-bundle ~2.3 -&gt; no matching package found.
      - sonata-project/admin-bundle 2.3.3 requires sensio/generator-bundle ~2.3 -&gt; no matching package found.
      - sonata-project/admin-bundle 2.3.2 requires sensio/generator-bundle ~2.3 -&gt; no matching package found.
      - sonata-project/admin-bundle 2.3.1 requires sensio/generator-bundle ~2.3 -&gt; no matching package found.
      - sonata-project/admin-bundle 2.3.0 requires sensio/generator-bundle ~2.3 -&gt; no matching package found.
      - Installation request for sonata-project/admin-bundle ^2.3 -&gt; satisfiable by sonata-project/admin-bundle[2.3.0, 2.3.1, 2.3.2, 2.3.3, 2.3.4, 2.3.5, 2.3.6, 2.3.7].
  
  Potential causes:
   - A typo in the package name
   - The package is not available in a stable-enough version according to your minimum-stability setting
     see &lt;https://groups.google.com/d/topic/composer-dev/_g3ASeIFlrc/discussion&gt; for more details.
  
  Read &lt;https://getcomposer.org/doc/articles/troubleshooting.md&gt; for further common problems.</code></pre>
  </div>
  </div>
  
  however I have installed sensio/generator-bundle
  what is the problem ? and how I can fix that ? </p>
  
  <p>my symfony is 3.0.1 </p>