Update _s.pot

Change "Posted on" string.
And add "by" string.
Related: #453, e24e53e
Merge pull request #507 from gatespace/update_pot

Update `_s.pot`.
Creates content-search.php and removes is_search() check from content.php
Merge pull request #512 from slobodan/content-search

First pass at creating a search-dedicated post template. Simplifies `content.php` and makes use of the template hierarchy.

Eventually we can think about removing more meta information, as appropriate.
_s: Document background color fallback.

A default background color is needed for any time there is no custom background color.
This happens to use the browser's default `#fff`, and is meant more as a reminder for theme authors.

See #515.
Minor spacing fix for main navigation

Just an itsy-bitsy space removal, no biggie, but needed :)
Merge pull request #517 from emiluzelac/patch-29

Minor spacing fix for main navigation props @emiluzelac
Revert the change to spacing in #517

Adds back in space for now. Props @lancewillett
Changed lone uppercase H to lower
Correcting some irregular capitalisation and coding standards issues
Undid my multiline function corrections
Merge pull request #524 from jacklenox/dev

Capitalisation and coding standards corrections - props @jacklenox
Add a non-breaking space to _s_post_nav().

Sometimes the title length of a previous or next post would cause
the arrow (larr/rarr) in the link to be wrapped to the next line.
Adding a non-breaking space between the title and the arrow will stick
it to the last word in the title.
Remove default widgets from sidebar
is_active_sidebar() check

Check to ensure sidebar is active before displaying #secondary
Remove unnecessary semicolon
Merge pull request #529 from Automattic/Remove-Default-Widgets

Remove default widgets from sidebar.

Closes #528.
_s: Use braces in all conditionals.

Formatting updates for file comment, conditional braces, and indentation.
_s: Simplify entry meta output

- Add entry-footer consistency between content-*.php files
- Move in a function _s_entry_meta() to avoid duplicate
Update README to be more consistent

Wrap all file paths in '`', capitalize properly, fix grammar.