convert ERC20Pausable to initializers

contracts/mocks/ERC20PausableMock.sol

 pragma solidity ^0.4.24;
 
+import "../Initializable.sol";
 import "../token/ERC20/ERC20Pausable.sol";
 import "./PauserRoleMock.sol";
 
 
 // mock class using ERC20Pausable
-contract ERC20PausableMock is ERC20Pausable, PauserRoleMock {
+contract ERC20PausableMock is Initializable, ERC20Pausable, PauserRoleMock {
 
   constructor(address initialAccount, uint initialBalance) public {
+    ERC20Pausable.initialize();
+
     _mint(initialAccount, initialBalance);
   }
 

contracts/token/ERC20/ERC20Pausable.sol

 pragma solidity ^0.4.24;
 
+import "../../Initializable.sol";
 import "./ERC20.sol";
 import "../../lifecycle/Pausable.sol";
 
@@ -8,7 +9,11 @@ import "../../lifecycle/Pausable.sol";
  * @title Pausable token
  * @dev ERC20 modified with pausable transfers.
  **/
-contract ERC20Pausable is ERC20, Pausable {
+contract ERC20Pausable is Initializable, ERC20, Pausable {
+
+  function initialize() public initializer {
+    Pausable.initialize();
+  }
 
   function transfer(
     address to,