To avoid having to move all the sponsors through the bootstrap 'row'
when adding a new "past sponsor" on top of the current stack, this
commit make the card rely on flexboxes instead of the bootstrap
internals.
This make sure that the body of the card always fit the row height and
the also make sure that the image always fit properly without having to
touch the inline css.
Signed-off-by: Thomas Perale <thomas.perale@mind.be>
Signed-off-by: Julien Olivain <ju.o@free.fr>
