Added slider display to Employer Showcase view

Signed-off-by: Joe Whitsitt <joe-whitsitt@uiowa.edu>
Added default border mixin (shadow and radius)

Signed-off-by: Joe Whitsitt <joe-whitsitt@uiowa.edu>
Added flexslider styles specific to the Employer Showcase slider display

Signed-off-by: Joe Whitsitt <joe-whitsitt@uiowa.edu>