convert Crowdsale to initializers

contracts/mocks/CrowdsaleMock.sol

@@ -0,0 +1,11 @@
+pragma solidity ^0.4.24;
+
+import "../Initializable.sol";
+import "../crowdsale/Crowdsale.sol";
+
+
+contract CrowdsaleMock is Initializable, Crowdsale {
+  constructor(uint256 rate, address wallet, IERC20 token) public Crowdsale(rate, wallet, token) {
+    Crowdsale.initialize(rate, wallet, token);
+  }
+}