fix import directories

contracts/payment/PullPayment.sol

@@ -1,7 +1,7 @@
 pragma solidity ^0.4.11;
 
 
-import '../SafeMath.sol';
+import '../math/SafeMath.sol';
 
 
 /**

contracts/token/BasicToken.sol

@@ -2,7 +2,7 @@ pragma solidity ^0.4.11;
 
 
 import './ERC20Basic.sol';
-import '../SafeMath.sol';
+import '../math/SafeMath.sol';
 
 
 /**

test/helpers/SafeMathMock.sol

@@ -1,7 +1,7 @@
 pragma solidity ^0.4.11;
 
 
-import '../../contracts/SafeMath.sol';
+import '../../contracts/math/SafeMath.sol';
 
 
 contract SafeMathMock {