convert RefundEscrow to initializers

contracts/crowdsale/distribution/RefundableCrowdsale.sol

@@ -26,7 +26,13 @@ contract RefundableCrowdsale is FinalizableCrowdsale {
    */
   constructor(uint256 goal) public {
     require(goal > 0);
-    _escrow = new RefundEscrow(wallet());
+
+    // conditional added to make initializer idempotent in case of diamond inheritance
+    if (address(_escrow) == address(0)) {
+      _escrow = new RefundEscrow();
+      _escrow.initialize(wallet());
+    }
+
     _goal = goal;
   }
 

contracts/mocks/RefundEscrowMock.sol

+pragma solidity ^0.4.24;
+
+import "../Initializable.sol";
+import "../payment/RefundEscrow.sol";
+
+contract RefundEscrowMock is Initializable, RefundEscrow {
+  constructor(address beneficiary) public {
+    RefundEscrow.initialize(beneficiary);
+  }
+}

contracts/payment/RefundEscrow.sol

 pragma solidity ^0.4.24;
 
+import "../Initializable.sol";
 import "./ConditionalEscrow.sol";
 import "../ownership/Secondary.sol";
 
@@ -10,7 +11,7 @@ import "../ownership/Secondary.sol";
  * The primary account may close the deposit period, and allow for either withdrawal
  * by the beneficiary, or refunds to the depositors.
  */
-contract RefundEscrow is Secondary, ConditionalEscrow {
+contract RefundEscrow is Initializable, Secondary, ConditionalEscrow {
   enum State { Active, Refunding, Closed }
 
   event Closed();
@@ -23,7 +24,10 @@ contract RefundEscrow is Secondary, ConditionalEscrow {
    * @dev Constructor.
    * @param beneficiary The beneficiary of the deposits.
    */
-  constructor(address beneficiary) public {
+  function initialize(address beneficiary) public initializer {
+    Secondary.initialize();
+    ConditionalEscrow.initialize();
+
     require(beneficiary != address(0));
     _beneficiary = beneficiary;
     _state = State.Active;

test/payment/RefundEscrow.test.js

@@ -9,7 +9,7 @@ require('chai')
   .use(require('chai-bignumber')(BigNumber))
   .should();
 
-const RefundEscrow = artifacts.require('RefundEscrow');
+const RefundEscrow = artifacts.require('RefundEscrowMock');
 
 contract('RefundEscrow', function ([_, primary, beneficiary, refundee1, refundee2]) {
   const amount = web3.toWei(54.0, 'ether');