Add increase and decrease approval functions to ERC827 with tests

contracts/token/ERC827.sol

@@ -78,4 +78,48 @@ contract ERC827 is StandardToken {
     return true;
   }
 
+  /**
+   * @dev Addition to StandardToken methods. Increase the amount of tokens that
+   * an owner allowed to a spender and execute a call with the sent data.
+   *
+   * approve should be called when allowed[_spender] == 0. To increment
+   * allowed value is better to use this function to avoid 2 calls (and wait until
+   * the first transaction is mined)
+   * From MonolithDAO Token.sol
+   * @param _spender The address which will spend the funds.
+   * @param _addedValue The amount of tokens to increase the allowance by.
+   * @param _data ABI-encoded contract call to call `_spender` address.
+   */
+  function increaseApproval(address _spender, uint _addedValue, bytes _data) public returns (bool) {
+    require(_spender != address(this));
+
+    super.approve(_spender, _addedValue);
+
+    require(_spender.call(_data));
+
+    return true;
+  }
+
+  /**
+   * @dev Addition to StandardToken methods. Decrease the amount of tokens that
+   * an owner allowed to a spender and execute a call with the sent data.
+   *
+   * approve should be called when allowed[_spender] == 0. To decrement
+   * allowed value is better to use this function to avoid 2 calls (and wait until
+   * the first transaction is mined)
+   * From MonolithDAO Token.sol
+   * @param _spender The address which will spend the funds.
+   * @param _subtractedValue The amount of tokens to decrease the allowance by.
+   * @param _data ABI-encoded contract call to call `_spender` address.
+   */
+  function decreaseApproval(address _spender, uint _subtractedValue, bytes _data) public returns (bool) {
+    require(_spender != address(this));
+
+    super.decreaseApproval(_spender, _subtractedValue);
+
+    require(_spender.call(_data));
+
+    return true;
+  }
+
 }