Load comments template only when comments are open or there's at least one comment

To be consistent with single.php and to ensure that an empty div (<div
id="comments" class="comments-area">) isn't outputted when both
comments are closed and there aren't any comments.
Merge pull request #132 from davidensinger/master

Load comments template only when comments are open or there's at least one comment in image.php and page.php
Fix indentation on comments block
Fix spacing and tabbing problems in page.php introduced in 413403827878875d1fd3505e442a0448d77120ff and 054aa194a7d86ee090836aad946aac04cc0e7fc8
_s: Simpler selector for lists within lists.
_s: Aggregate translation strings and make comment edit links easier to
style.
_s: Enable live preview for Header Text Color in Customizer. Change also
removes an !important declaration in Custom Header CSS rules.
_s: Formatting changes:

- Reduce element comments to either the element id or the first element
class.
- Tabs > Spaces.
- Improve adherence to formatting guidelines.
_s: Introduce a default for clearing floats.

Selectors provide clearing out of the box for the site container,
header, footer, main container, content container, entry content, and
comment content.

Also, theme developers can optionally use .clear as a utility class. Or
delete it.

For more information about the philosophy behind the approach of
selecting class elements, see
http://24ways.org/2012/a-harder-working-class/

Fixes #88.
Remove blank tabs/trailing whitespace
Add an identifier into style.css that will allow us — the WordPress.com Theme Team — to easily search for themes that have been built with _s. Now there will be no more scratching our heads whenever someone asks, "What have you built with _s?" :)
Changed nav closing tag comment to indicate CSS id
Merge pull request #175 from braden337/master

_s: site-navigation is an id not a class, silly!
_s: Use .screen-reader-text rather than .assistive-text.

With 3.6 introducing many HTML5 improvements the need for custom
searchform and comment templates will vanish. To cope with core's
.screen-reader-text class, let's make the switch early.

Commit also adds core's focus styles for screen reader texts, so they
can actually be used.
Image navigation improvements

Add a navigation role, replace spans with divs and also add a
'.meta-nav' for both previous and next image links.
Merge pull request #179 from eduardozulian/patch/image-navigation

Image navigation improvements