Fix popover not passing element to content function

Created by: zkwentz

Given the following example code:

$(document).popover({
   trigger: 'hover',
   viewport: '#containerOverlay',
   placement: 'auto top',
   selector: '.leaderboard-popover',
   html: true,
   animation: true,
   delay: {
       show: 250,
       hide: 100
   },
   content: function(element) {
   console.log('passed element',element);
   }
});

console will output the following: passed element undefined.

With the inclusion of this to content.call we pass with context, and our element is defined. Console now outputs the following: passed element <span class="display popover">....</span>