I've found that the widget is not being wrapped by the before/after_widget functions so it wont be styled using the code set up in in functions php. I was able to fix the problem by making the following changes.
In /lib/IvyCatTestimonialsWidget.php change line 104 from:
echo IvyCatTestimonials::do_testimonials( $atts );
echo $args[ 'before_widget' ]; echo IvyCatTestimonials::do_testimonials( $atts ); echo $args[ 'after_widget' ];
Also noticed that before/after_title are not working either. tried a couple of different fixes with no luck... just for reference this is what I tried...
1. changing line 94 from:
'title' => $title ,
'title' => $before_title . $title . $after_title,
2. commenting out $title from the $args array and adding
if ( $title) echo $before_title . $title . $after_title;
after echo $before_widget;