Merge git://github.com/jdevalk/wordpress-seo into duplicate-sitemaps

Conflicts:
	readme.txt
Merge pull request #498 from jrfnl/duplicate-sitemaps

Fix for sitemap issue which caused all pages of a split sitemap to be the same
Fixed a bug in the WPSEO tour in WP Network installs

Fixes #537
Merge branch 'master' of git://github.com/jdevalk/wordpress-seo

Conflicts:
	readme.txt