Twenty Fifteen: Use a p for the site description for a better experience when using a screenreader.

Props rianrietveld, fixes #30057, see #30065.

Built from https://develop.svn.wordpress.org/trunk@30009


git-svn-id: http://core.svn.wordpress.org/trunk@30009 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fifteen: removing Skype from the list of social links is easier than adding skype to $allowed_protocols.

Props iamtakashi, fixes #30059.


Built from https://develop.svn.wordpress.org/trunk@30010


git-svn-id: http://core.svn.wordpress.org/trunk@30010 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fifteen: darken up the post navigation with thumbnail for better a11y.

Props davidakennedy, fixes #30069.

Built from https://develop.svn.wordpress.org/trunk@30011


git-svn-id: http://core.svn.wordpress.org/trunk@30011 1a063a9b-81f0-0310-95a4-ce76da25c4cd