Merge pull request #341 from lsaether/master

Added contracts/token/BurnableToken.sol

contracts/token/BurnableToken.sol

@@ -0,0 +1,27 @@
+pragma solidity ^0.4.13;
+
+import './StandardToken.sol';
+
+/**
+ * @title Burnable Token
+ * @dev Token that can be irreversibly burned (destroyed).
+ */
+contract BurnableToken is StandardToken {
+
+    /**
+     * @dev Burns a specific amount of tokens.
+     * @param _value The amount of token to be burned.
+     */
+    function burn(uint _value)
+        public
+    {
+        require(_value > 0);
+
+        address burner = msg.sender;
+        balances[burner] = balances[burner].sub(_value);
+        totalSupply = totalSupply.sub(_value);
+        Burn(burner, _value);
+    }
+
+    event Burn(address indexed burner, uint indexed value);
+}