Make sure options exist after activation

- Avoid extra db query if option doesn't exist
- Make sure the option as saved on activation will contain translated defaults
Fix file editing on multi-site
Merge branch 'master' into Small-fixes
Remove the extra blog name added to the title by woo_title()
Fixes #1308
Set rssafter to empty string on test_embed_rss() test
Check if get_queried_object_id is not 0 before enqueueing wp_enqueue_media
Change log update
Change log update & version increment
Added release date to change log
Removed extra linebreaks from changelog
Format unix timestamp to string in sitemap.
Fixes #1311
Merge branch 'master' of git://github.com/Yoast/wordpress-seo into Issue-1302
`is_feed()` check is already done in embed_rss() function, no need to double it
Mini-improvements to embed_rss test
Add clarification comment to function
Merge pull request #1303 from jrfnl/Issue-1302

Fix file editing on multi-site
Prevent `DateTime` borking if int is passed to it.

`null` will make it return the current date & time
Minified the metabox.js file

Fixes issue #1312, #1313
Undo unit test update
Merge pull request #1316 from jrfnl/Mini-fixes

Mini fixes, props @jrfnl