Tweak homepage theme (#542)

* Make athens banner smaller

This helps people see that there is more content below the athens logo, otherwise
the most prominent thing they see is the next arrow >
and they miss our homepage content.

* Make home link friendly for previews

Right now when viewing a preview of our docs site, when I click on the home logo
I end up on our live site. This makes the home logo go to the root of the
current site instead, which is more friendly for testing docs locally
or previewing a PR.

docs/content/_index.md

@@ -3,7 +3,8 @@ title: "Intro"
 date: 2018-02-11T16:52:23-05:00
 ---
 
-![Athens logo](/banner.png)
+<img src="/banner.png" width="600" alt="Athens Logo"/>
+
 
 ## Welcome to Athens
 

docs/themes/hugo-theme-learn/layouts/partials/logo.html

@@ -1,3 +1,3 @@
-<a id="logo" href="https://docs.gomods.io">
+<a id="logo" href="/">
   <img src="/logo@2x.png"></img>
 </a>

docs/themes/hugo-theme-learn/static/css/theme.css

@@ -343,7 +343,7 @@ textarea:focus, input[type="email"]:focus, input[type="number"]:focus, input[typ
     border: 1px solid #ccc;
 }
 #body .padding {
-    padding: 3rem 6rem;
+    padding: 1rem 6rem 3rem 6rem;
 }
 @media only all and (max-width: 59.938em) {
     #body .padding {