Letterman Birkit diary

Samantha Birkitt’s diary is full of secrets Robert Halderman didn’t want to read, the NY Post reavels (via PopEater). Although earlier reports claim Birkitt and Letterman’s relationship ended before his son Harry was born in 2003, they’ve had romantic getaways as recent as last fall. Here’s some of the juicy details: Birkett left Halderman at…