For me it works with
tags$script("$('ul.nav-tabs').on('click', 'li', function(e) { ga('send', 'event', 'widget', 'nav-tabs link', $(e.currentTarget).children('a').data('value'));});")
It need to be in the end of your ui, or at least come after you defined your tabset, and google-analytics.js need to be loaded before. It sends the name (stored in 'data-value') of the clicked tabPanel to ga.
adding following to google-analytics.js should also work, but I haven't tested it and might be a bit less efficient as it listens to the whole document.
$(document).on('click', ''ul.nav-tabs' > li', function(e) { ga('send', 'event', 'widget', 'nav-tabs link', $(e.currentTarget).children('a').data("value")); });
/Lukas