_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.