Add Summer Reading link to topnav
Add Summer Reading link to topnav

Add link to Summer Reading site to topnav, in the dash area. Link is
present when user is logged in and not logged in.

Signed-off-by: Jeff Godin <7b658ab2e5573260a7dc1c722b8df4a45dfe4eff@tadl.org>

tadl/Evergreen_templates_tadlskin