In addition to creating additional dimension, Wordpress does keep your original image. Your original image is in this link http://whatweblog.com/wp-content/uploads/2015/05/hue.gif
So, instead of stopping Wordpress from creating additional dimension, you should retrieve the full image when displaying the featured image. You can get the full image with this -
the_post_thumbnail('full');
In your case, change
<?php the_post_thumbnail('featured-image', array('class' => 'featured-full-width-top')); ?>
to
<?php the_post_thumbnail('full', array('class' => 'featured-full-width-top')); ?>
Remove Thumbnail Generation
See http://wordpress.stackexchange.com/a/91170/23214https://wordpress.stackexchange.com/a/91170/23214
Another easier option I think works is going to your Settings-->Media and setting each box for width and height to 0