move erc20 and standardtoken to token folder

contracts/test-helpers/StandardTokenMock.sol

@@ -1,5 +1,5 @@
 pragma solidity ^0.4.4;
-import '../StandardToken.sol';
+import '../token/StandardToken.sol';
 
 // mock class using StandardToken
 contract StandardTokenMock is StandardToken {

contracts/token/CrowdsaleToken.sol

@@ -1,6 +1,6 @@
 pragma solidity ^0.4.4;
 
-import "../StandardToken.sol";
+import "./StandardToken.sol";
 
 /*
  * Simple ERC20 Token example, with crowdsale token creation

contracts/token/SimpleToken.sol

@@ -1,6 +1,6 @@
 pragma solidity ^0.4.4;
 
-import "../StandardToken.sol";
+import "./StandardToken.sol";
 
 /*
  * Very simple ERC20 Token example, where all tokens are pre-assigned

contracts/StandardToken.sol → contracts/token/StandardToken.sol

@@ -1,7 +1,7 @@
 pragma solidity ^0.4.4;
 
 import './ERC20.sol';
-import './SafeMath.sol';
+import '../SafeMath.sol';
 
 /**
  * ERC20 token