Docs: format inline <code> blocks better.

It seems like we're using these differently than most readthedocs.org
users.  Remove the borders and padding so they work better inline, and
prevent confusing word wraps.

Documentation/extra_style.css

@@ -0,0 +1,8 @@
+p code {
+    border: 0;
+    padding: 0 2px 0 2px;
+    font-size: 100%;
+    white-space: nowrap;
+    color: #a04040;
+    letter-spacing: -1px;
+}

mkdocs.yml

@@ -7,6 +7,8 @@ repo_url: https://github.com/apenwarr/redo
 edit_uri: edit/master/Documentation
 extra_javascript:
   - fetchcode.js
+extra_css:
+  - extra_style.css
 
 pages:
   - Introduction: index.md