fix roles initialization bug

contracts/examples/StandardToken.sol

@@ -23,10 +23,10 @@ contract StandardToken is Initializable, ERC20Detailed, ERC20Mintable, ERC20Paus
         }
 
         // Initialize the minter and pauser roles, and renounce them
-        ERC20Mintable.initialize(address(this));
+        ERC20Mintable.initialize(msg.sender);
         renounceMinter();
 
-        ERC20Pausable.initialize(address(this));
+        ERC20Pausable.initialize(msg.sender);
         renouncePauser();
 
         // Add the requested minters and pausers (this can be done after renouncing since

contracts/token/ERC20/StandaloneERC20.sol

@@ -21,10 +21,10 @@ contract StandaloneERC20 is Initializable, ERC20Detailed, ERC20Mintable, ERC20Pa
         _mint(initialHolder, initialSupply);
 
         // Initialize the minter and pauser roles, and renounce them
-        ERC20Mintable.initialize(address(this));
+        ERC20Mintable.initialize(msg.sender);
         renounceMinter();
 
-        ERC20Pausable.initialize(address(this));
+        ERC20Pausable.initialize(msg.sender);
         renouncePauser();
 
         // Add the requested minters and pausers (this can be done after renouncing since

contracts/token/ERC721/StandaloneERC721.sol

@@ -21,10 +21,10 @@ contract StandaloneERC721
         ERC721Metadata.initialize(name, symbol);
 
         // Initialize the minter and pauser roles, and renounce them
-        ERC721MetadataMintable.initialize(address(this));
+        ERC721MetadataMintable.initialize(msg.sender);
         renounceMinter();
 
-        ERC721Pausable.initialize(address(this));
+        ERC721Pausable.initialize(msg.sender);
         renouncePauser();
 
         // Add the requested minters and pausers (this can be done after renouncing since