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

Props rianrietveld, fixes #30057, see #30065.


git-svn-id: https://develop.svn.wordpress.org/trunk@30009 602fd350-edb4-49c9-b593-d223f7449a82
Twenty Fifteen: removing Skype from the list of social links is easier than adding skype to $allowed_protocols.

Props iamtakashi, fixes #30059.



git-svn-id: https://develop.svn.wordpress.org/trunk@30010 602fd350-edb4-49c9-b593-d223f7449a82
Twenty Fifteen: darken up the post navigation with thumbnail for better a11y.

Props davidakennedy, fixes #30069.


git-svn-id: https://develop.svn.wordpress.org/trunk@30011 602fd350-edb4-49c9-b593-d223f7449a82