Fix duplication on project pages

Issue #26

source/_includes/projects/skills.html.twig

@@ -0,0 +1,11 @@
+{% if page.skills %}
+    <div class="project--skills">
+        <h2>Skills</h2>
+
+        <ul>
+            {% for item in page.skills|sort %}
+                <li>{{ site.skills[item].title }}</li>
+            {% endfor %}
+        </ul>
+    </div>
+{% endif %}