add a short_bio div

It's static for the time being
add ids to the person divs
add a right arrow to the short bio

That way you know who's biography you are reading.
add a close button to the bio
show short bio when hovering over the person's name or photo
(minor) put shortPerson() in CamelCase for consistency
make closeShortBioButton() use closeShortBio()
don't close the short bio if the user moves the mouse to it
always show a pointer when hovering a person
make the show and close ShortBio functions generic
add bios for Stalin, Roosevelt and Churchill
move short bios into each person's div
make ShortBio a class

Fix a bug in the process when multiple shortBio were beeing shown at
the same time.  Previously they were sharing the timeout, so only the
last one went out onMouseOut.
make the close button use the ShortBio class as well