convert PauserRole to initializers

contracts/access/roles/PauserRole.sol

 pragma solidity ^0.4.24;
 
+import "../../Initializable.sol";
 import "../Roles.sol";
 
 
-contract PauserRole {
+contract PauserRole is Initializable {
   using Roles for Roles.Role;
 
   event PauserAdded(address indexed account);
@@ -11,7 +12,7 @@ contract PauserRole {
 
   Roles.Role private pausers;
 
-  constructor() public {
+  function initialize() public initializer {
     pausers.add(msg.sender);
   }
 

contracts/mocks/PauserRoleMock.sol

 pragma solidity ^0.4.24;
 
+import "../Initializable.sol";
 import "../access/roles/PauserRole.sol";
 
 
-contract PauserRoleMock is PauserRole {
+contract PauserRoleMock is Initializable, PauserRole {
+  constructor() public {
+    PauserRole.initialize();
+  }
+
   function removePauser(address account) public {
     _removePauser(account);
   }