convert ERC20

contracts/mocks/ERC20Mock.sol

 pragma solidity ^0.4.24;
 
+import "../Initializable.sol";
 import "../token/ERC20/ERC20.sol";
 
 
 // mock class using ERC20
-contract ERC20Mock is ERC20 {
+contract ERC20Mock is Initializable, ERC20 {
 
   constructor(address initialAccount, uint256 initialBalance) public {
     _mint(initialAccount, initialBalance);

contracts/token/ERC20/ERC20.sol

 pragma solidity ^0.4.24;
 
+import "../../Initializable.sol";
 import "./IERC20.sol";
 import "../../math/SafeMath.sol";
 
@@ -11,7 +12,7 @@ import "../../math/SafeMath.sol";
  * https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md
  * Originally based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
  */
-contract ERC20 is IERC20 {
+contract ERC20 is Initializable, IERC20 {
   using SafeMath for uint256;
 
   mapping (address => uint256) private _balances;