Replace constant with view/pure

contracts/token/BasicToken.sol

@@ -35,7 +35,7 @@ contract BasicToken is ERC20Basic {
   * @param _owner The address to query the the balance of.
   * @return An uint256 representing the amount owned by the passed address.
   */
-  function balanceOf(address _owner) public constant returns (uint256 balance) {
+  function balanceOf(address _owner) public view returns (uint256 balance) {
     return balances[_owner];
   }
 

contracts/token/ERC20.sol

@@ -9,7 +9,7 @@ import './ERC20Basic.sol';
  * @dev see https://github.com/ethereum/EIPs/issues/20
  */
 contract ERC20 is ERC20Basic {
-  function allowance(address owner, address spender) public constant returns (uint256);
+  function allowance(address owner, address spender) public view returns (uint256);
   function transferFrom(address from, address to, uint256 value) public returns (bool);
   function approve(address spender, uint256 value) public returns (bool);
   event Approval(address indexed owner, address indexed spender, uint256 value);

contracts/token/ERC20Basic.sol

@@ -8,7 +8,7 @@ pragma solidity ^0.4.18;
  */
 contract ERC20Basic {
   uint256 public totalSupply;
-  function balanceOf(address who) public constant returns (uint256);
+  function balanceOf(address who) public view returns (uint256);
   function transfer(address to, uint256 value) public returns (bool);
   event Transfer(address indexed from, address indexed to, uint256 value);
 }

contracts/token/StandardToken.sol

@@ -57,7 +57,7 @@ contract StandardToken is ERC20, BasicToken {
    * @param _spender address The address which will spend the funds.
    * @return A uint256 specifying the amount of tokens still available for the spender.
    */
-  function allowance(address _owner, address _spender) public constant returns (uint256) {
+  function allowance(address _owner, address _spender) public view returns (uint256) {
     return allowed[_owner][_spender];
   }
 

contracts/token/TokenVesting.sol

@@ -91,7 +91,7 @@ contract TokenVesting is Ownable {
    * @dev Calculates the amount that has already vested but hasn't been released yet.
    * @param token ERC20 token which is being vested
    */
-  function releasableAmount(ERC20Basic token) public constant returns (uint256) {
+  function releasableAmount(ERC20Basic token) public view returns (uint256) {
     return vestedAmount(token).sub(released[token]);
   }
 
@@ -99,7 +99,7 @@ contract TokenVesting is Ownable {
    * @dev Calculates the amount that has already vested.
    * @param token ERC20 token which is being vested
    */
-  function vestedAmount(ERC20Basic token) public constant returns (uint256) {
+  function vestedAmount(ERC20Basic token) public view returns (uint256) {
     uint256 currentBalance = token.balanceOf(this);
     uint256 totalBalance = currentBalance.add(released[token]);