Move password change to new Security tab

app/views/shared/_main_nav.html.erb

@@ -13,6 +13,10 @@
         <%= link_to "Donations", donations_path,
               class: @current_section == :contributions ? "active" : nil %>
       </li>
+      <li>
+        <%= link_to "Security", security_path,
+              class: @current_section == :security ? "active" : nil %>
+      </li>
     </ul>
   </div>
 </nav>