coding style update re: javadocs

i2p2www/pages/site/get-involved/guides/dev-guidelines.html

 {% extends "global/layout.html" %}
 {% block title %}{{ _('Developer Guidelines and Coding Style') }}{% endblock %}
-{% block lastupdated %}{% trans %}April 2016{% endtrans %}{% endblock %}
+{% block lastupdated %}{% trans %}January 2017{% endtrans %}{% endblock %}
 {% block content %}
 <p>{% trans newdevs=site_url('get-involved/guides/new-developers') -%}
 Read the <a href="{{ newdevs }}">new developers guide</a> first.
@@ -131,6 +131,12 @@ All new public and package-private classes and methods require Javadocs. Add @si
 Javadocs for new private methods are desirable.
 {%- endtrans %}</li>
 <li>{% trans -%}
+For any Javadocs added, there must not be any doclint errors or warnings.
+Run 'ant javadoc' with Oracle Java 8 or higher to check.
+All params must have @param lines, all non-void methods must have @return lines,
+all exceptions declared thrown must have @throws lines, and no HTML errors.
+{%- endtrans %}</li>
+<li>{% trans -%}
 Classes in core/ (i2p.jar) and portions of i2ptunnel are part of our official API.
 There are several out-of-tree plugins and other applications that rely on this API.
 Be careful not to make any changes that break compatibility.