Merge pull request #441 from arifcakiroglu/source

Update hexdex to include Istanbul

Author: arifcakiroglu

hexdex.html

@@ -122,6 +122,9 @@ <h1 data-i18n="hexdex-h1">Hexdex</h1>
           <a class="imglink" href="https://github.com/nodeschool/sanfrancisco/" title="San Francisco">
             <img class="hex" src="images/nodeschool-sf.svg" alt="San Francsico Hexagon">
           </a>
+          <a class="imglink" href="https://github.com/nodeschool/istanbul/" title="Istanbul">
+            <img class="hex" src="images/nodeschool-istanbul.svg" alt="Istanbul Hexagon">
+          </a>
           <a class="imglink" href="https://github.com/nodeschool/campinas" title="Campinas">
             <img class="hex" src="/images/nodeschool-campinas.svg" alt="Campinas Hexagon">
           </a>