Update all solidity versions to 0.4.18

contracts/Bounty.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 import './payment/PullPayment.sol';

contracts/DayLimit.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 /**
  * @title DayLimit

contracts/ECRecovery.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 /**

contracts/LimitBalance.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 /**

contracts/MerkleProof.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 /*
  * @title MerkleProof

contracts/ReentrancyGuard.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 /**
  * @title Helps contracts guard agains rentrancy attacks.

contracts/crowdsale/CappedCrowdsale.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 import '../math/SafeMath.sol';
 import './Crowdsale.sol';

contracts/crowdsale/Crowdsale.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 import '../token/MintableToken.sol';
 import '../math/SafeMath.sol';

contracts/crowdsale/FinalizableCrowdsale.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 import '../math/SafeMath.sol';
 import '../ownership/Ownable.sol';

contracts/crowdsale/RefundVault.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 import '../math/SafeMath.sol';
 import '../ownership/Ownable.sol';

contracts/crowdsale/RefundableCrowdsale.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 import '../math/SafeMath.sol';

contracts/examples/SampleCrowdsale.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 import "../crowdsale/CappedCrowdsale.sol";
 import "../crowdsale/RefundableCrowdsale.sol";

contracts/examples/SimpleToken.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 import "../token/StandardToken.sol";

contracts/lifecycle/Destructible.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 import "../ownership/Ownable.sol";

contracts/lifecycle/Migrations.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 import '../ownership/Ownable.sol';

contracts/lifecycle/Pausable.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 import "../ownership/Ownable.sol";

contracts/lifecycle/TokenDestructible.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 import "../ownership/Ownable.sol";

contracts/math/Math.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 /**
  * @title Math

contracts/math/SafeMath.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 /**

contracts/ownership/CanReclaimToken.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 import "./Ownable.sol";
 import "../token/ERC20Basic.sol";

contracts/ownership/Claimable.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 import './Ownable.sol';

contracts/ownership/Contactable.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 import './Ownable.sol';
 

contracts/ownership/DelayedClaimable.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 import './Claimable.sol';

contracts/ownership/HasNoContracts.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 import "./Ownable.sol";
 

contracts/ownership/HasNoEther.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 import "./Ownable.sol";
 

contracts/ownership/HasNoTokens.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 import "./CanReclaimToken.sol";
 

contracts/ownership/NoOwner.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 import "./HasNoEther.sol";
 import "./HasNoTokens.sol";

contracts/ownership/Ownable.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 /**

contracts/payment/PullPayment.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 import '../math/SafeMath.sol';

contracts/payment/SplitPayment.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 import '../math/SafeMath.sol';
 

contracts/token/BasicToken.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 import './ERC20Basic.sol';

contracts/token/BurnableToken.sol

-pragma solidity ^0.4.13;
+pragma solidity ^0.4.18;
 
 import './StandardToken.sol';
 

contracts/token/DetailedERC20.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 import './ERC20.sol';
 

contracts/token/ERC20.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 import './ERC20Basic.sol';

contracts/token/ERC20Basic.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 /**

contracts/token/MintableToken.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 import './StandardToken.sol';

contracts/token/PausableToken.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 import './StandardToken.sol';
 import '../lifecycle/Pausable.sol';

contracts/token/SafeERC20.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 import './ERC20Basic.sol';
 import './ERC20.sol';

contracts/token/StandardToken.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 import './BasicToken.sol';

contracts/token/TokenTimelock.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 
 import './ERC20Basic.sol';

contracts/token/TokenVesting.sol

-pragma solidity ^0.4.11;
+pragma solidity ^0.4.18;
 
 import './ERC20Basic.sol';
 import './SafeERC20.sol';