Define ajaxurl in the customizer.

props celloexpressions.
see #25866.

git-svn-id: https://develop.svn.wordpress.org/trunk@26082 602fd350-edb4-49c9-b593-d223f7449a82
Remove the code for setting ajaxurl from Twenty Fourteen.

props celloexpressions.
fixes #25866.

git-svn-id: https://develop.svn.wordpress.org/trunk@26083 602fd350-edb4-49c9-b593-d223f7449a82