BurnableToken doesn't fire Transfer event

[rstormsf]

• 📈 This is a feature request.

🎉 Description

As a user, I'd expect that BurnableToken when called burn(uint _value) method, it should fire
Transfer(msg.sender, address(0), value); event.

https://github.com/OpenZeppelin/zeppelin-solidity/blob/master/contracts/token/ERC20/BurnableToken.sol#L18

the same as MintableToken does when it fires mint(to, value)
https://github.com/OpenZeppelin/zeppelin-solidity/blob/master/contracts/token/ERC20/MintableToken.sol#L35

    Transfer(address(0), _to, _amount);

Thoughts?

[androolloyd]

Is it a transfer though, it reads to me as a complete destruction of the burned token, rather than movement of it to a 0 address.

[AugustoL]

I think it should have it! we had to change the burn method in the LifToken implementation to add the burn function.

[AugustoL]

@rstormsf can you go ahead and create the PR? assign me as reviewer pls.

[rstormsf]

@AugustoL done