convert CapperRole and SignerRole to initializers

contracts/access/roles/CapperRole.sol

@@ -1,9 +1,10 @@
 pragma solidity ^0.4.24;
 
+import "../../Initializable.sol";
 import "../Roles.sol";
 
 
-contract CapperRole {
+contract CapperRole is Initializable {
   using Roles for Roles.Role;
 
   event CapperAdded(address indexed account);
@@ -11,7 +12,7 @@ contract CapperRole {
 
   Roles.Role private cappers;
 
-  constructor() public {
+  function initialize() public initializer {
     cappers.add(msg.sender);
   }
 

contracts/access/roles/SignerRole.sol

@@ -1,9 +1,10 @@
 pragma solidity ^0.4.24;
 
+import "../../Initializable.sol";
 import "../Roles.sol";
 
 
-contract SignerRole {
+contract SignerRole is Initializable {
   using Roles for Roles.Role;
 
   event SignerAdded(address indexed account);
@@ -11,7 +12,7 @@ contract SignerRole {
 
   Roles.Role private signers;
 
-  constructor() public {
+  function initialize() public initializer {
     signers.add(msg.sender);
   }
 

contracts/mocks/CapperRoleMock.sol

@@ -1,9 +1,14 @@
 pragma solidity ^0.4.24;
 
+import "../Initializable.sol";
 import "../access/roles/CapperRole.sol";
 
 
-contract CapperRoleMock is CapperRole {
+contract CapperRoleMock is Initializable, CapperRole {
+  constructor() public {
+    CapperRole.initialize();
+  }
+
   function removeCapper(address account) public {
     _removeCapper(account);
   }

contracts/mocks/SignerRoleMock.sol

@@ -1,9 +1,14 @@
 pragma solidity ^0.4.24;
 
+import "../Initializable.sol";
 import "../access/roles/SignerRole.sol";
 
 
-contract SignerRoleMock is SignerRole {
+contract SignerRoleMock is Initializable, SignerRole {
+  constructor() public {
+    SignerRole.initialize();
+  }
+
   function removeSigner(address account) public {
     _removeSigner(account);
   }