Added the oldest sovereign country in the world

### San Marino

Claims to be the oldest surviving sovereign state and constitutional republic in the world.

Legend has it that Marinus left Rab, then the Roman colony of Arba, in 257 when the future emperor, Diocletian, issued a decree calling for the reconstruction of the city walls of Rimini, which had been destroyed by Liburnian pirates.[Source]

[Source]:http://en.wikipedia.org/wiki/San_Marino