Add tab to indent 404.php(L43 to L45).
_s: Add context for translations and styles.

The referenced items are decisions we made for `_s`, that a re likely to be brought up again in pull requests or issues. Since our stance on them is not likely to change any time soon, let's include them in the Contributing FAQs.

See #464.
Merge pull request #463 from gatespace/formating-source-code

Indent multiline PHP code.