why-zulip: Include cartoon of Julia Evans.

static/styles/landing-page.css

@@ -1897,6 +1897,18 @@ nav ul li.active::after {
     z-index: 1;
 }
 
+#why-zulip-padded-content {
+    padding-top: 0px;
+}
+
+#why-zulip-hero {
+    padding-bottom: 0px;
+}
+
+#cartoon-caption {
+    margin-top: -45px;
+}
+
 /* -- hello page styling -- */
 .portico-landing.hello .apps .screen {
     display: inline-block;

templates/zerver/why-zulip.html

@@ -15,11 +15,9 @@
 {% include 'zerver/landing_nav.html' %}
 
 <div class="portico-landing why-page">
-    <div class="hero small-hero">
-        <h1 class="center">{% trans %}Why Zulip?{% endtrans %}</h1>
-    </div>
-    <div class="main">
-        <div class="padded-content">
+    <div class="hero small-hero" id="why-zulip-hero"></div>
+    <div class="main">"
+        <div class="padded-content" id="why-zulip-padded-content">
             <div class="inner-content">
                 {{ render_markdown_path('zerver/why-zulip.md') }}
             </div>

templates/zerver/why-zulip.md

@@ -1,3 +1,7 @@
+![why zulip cartoon by Jessica Evans](/static/images/why-zulip/cartoon.png)
+
+<center id="cartoon-caption">Explanation of Zulip by [Julia Evans](https://twitter.com/b0rk)</center>
+
 Zulip is not just a “better Slack”, in the same way that iPods were not just
 “better CD players”. Zulip’s topic-based threading changes what is possible
 in chat. If you haven’t seen Zulip in action, log on to our developers’