Twenty Fifteen: JSHint fixes.
 * Define global variables set by wp_localize_script().
 * Remove currently unused $ variable.
 * Use dot notation when appropriate.
 * Update Gruntfile.js to ignore the html5 shiv.
see #29799.


git-svn-id: https://develop.svn.wordpress.org/trunk@29893 602fd350-edb4-49c9-b593-d223f7449a82