Error: Contract `FiatTokenV1` is not upgrade safe

contracts/v1/FiatTokenV1.sol:58: Variable `totalSupply_` is assigned an initial value
  Move the assignment to the initializer
  https://zpl.in/upgrades/error-004

contracts/v1/Pausable.sol:49: Variable `paused` is assigned an initial value
  Move the assignment to the initializer
  https://zpl.in/upgrades/error-004

contracts/v1/Ownable.sol:28: Contract `Ownable` has a constructor
  Define an initializer instead
  https://zpl.in/upgrades/error-001

contracts/util/Address.sol:186: Use of delegatecall is not allowed
  https://zpl.in/upgrades/error-002
