cleanup formatting of some sidebar items

doc/_templates/indexsidebar.html

@@ -20,12 +20,14 @@ Index</a>, or install it with:{%endtrans%}</p>
 <h3>{%trans%}Questions? Suggestions?{%endtrans%}</h3>
 
 <p>{%trans%}Join the <a href="http://groups.google.com/group/sphinx-users">sphinx-users</a> mailing list on Google Groups:{%endtrans%}</p>
+<div class="subscribeformwrapper">
 <form action="http://groups.google.com/group/sphinx-users/boxsubscribe"
-      style="padding-left: 0.5em">
-  <input type="text" name="email" value="your@email" style="font-size: 90%; width: 120px"
-         onfocus="$(this).val('');"/>
-  <input type="submit" name="sub" value="Subscribe" style="font-size: 90%; width: 70px"/>
+      class="subscribeform">
+  <input type="text" name="email" value="your@email"
+         onfocus="$(this).val('');" />
+  <input type="submit" name="sub" value="Subscribe" />
 </form>
+</div>
 <p>{%trans%}or come to the <tt>#sphinx-doc</tt> channel on FreeNode.{%endtrans%}</p>
 <p>{%trans%}You can also open an issue at the
   <a href="https://github.com/sphinx-doc/sphinx/issues">tracker</a>.{%endtrans%}</p>