update getcomposer link (#629)

Author: Arhell

install.html

@@ -27,7 +27,7 @@ <h4>Follow QuickStart Guide to Install and execute your first test in 6 easy
     <div class="col-sm-6 col-lg-6">
       <div class="page">
         <h3>Composer <small><i>(recommended)</i></small></h3>
-        <p>Install a <a href="http://getcomposer.org">Composer</a> to your project's root</p>
+        <p>Install a <a href="https://getcomposer.org">Composer</a> to your project's root</p>
         <p>Run</p>
         <div class="highlight">
           <pre><code>composer require codeception/codeception --dev</code></pre>