Postagram, a new iOS app and service launched today by start-up Sincerely, lets users send physical postcards of photos saved in their Instagram account. Postcards sent through Postagram cost $.99 (users who download the app and create an account today will get one free postcard credit) and will be delivered within 2 to 5 days to addresses in the U.S. and a little longer for postcards delivered outside of the U.S. While users can add text to postcards, the maximum allowed is only 140 characters similar to Twitter. Each postcard automatically includes the name and Instagram profile photo of the sender. Postagram’s postcard creation and mailing service is also available…