[RCD-37] ChangeLog: Add 1.3.1 release
[RCD-37] ChangeLog: Add 1.3.1 release

input-output-hk/pos-haskell-prototype,input-output-hk/cardano-sl,input-output-hk/pos-haskell-prototype,input-output-hk/cardano-sl,input-output-hk/pos-haskell-prototype,input-output-hk/cardano-sl,input-output-hk/cardano-sl