add contents of nonfunctional chapter

Author: LEEHYUKJOO

_includes/developing-flows-toc.html

@@ -8,7 +8,7 @@
             <li {% if page.url == "/docs/developing-flows/implementation" %}class="active"{% endif %}><a href="/docs/developing-flows/implementation">Implementation</a></li>
             <li {% if page.url == "/docs/developing-flows/readability" %}class="active"{% endif %}><a href="/docs/developing-flows/readability">Readability</a></li>
             <li {% if page.url == "/docs/developing-flows/multiple-developers" %}class="active"{% endif %}><a href="/docs/developing-flows/multiple-developers">Project</a></li>
-            <li {% if page.url == "/docs/developing-flows/non-functional" %}class="active"{% endif %}><a href="/docs/developing-flows/non-functional">Strict non-functional requirements</a></li>
+            <li {% if page.url == "/docs/developing-flows/non-functional" %}class="active"{% endif %}><a href="/docs/developing-flows/non-functional">Non-functional requirements</a></li>
         </ul>
     </li>
 </ul>