Suggesting updates on the doc of DSToken.transferFrom

Hi,

The function `DSToken.transferFrom` emits an event `Transfer`, which is not documented in the README doc.

https://github.com/dapphub/ds-token/blob/16f187acc15dd839589be60173ad1ebd0716eb82/src/token.sol#L80

A potential fix could be adding "Emits a `Transfer` event" to the README doc.

Furthermore, function `DSToken.transfer` calls the function `transferFrom`. So it also emits the event `Transfer`.

https://github.com/dapphub/ds-token/blob/16f187acc15dd839589be60173ad1ebd0716eb82/src/token.sol#L63

A potential fix could be also adding "Emits a `Transfer` event" to this function in the README doc.

Could you please check it?

Thanks.